MAN page from Rawhide fetchmail-7.0.0-47.82.x86_64.rpm

FETCHMAIL

Section: fetchmail reference manual (1)
Updated: 2025-10-10
Index

 

NAME

fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server

 

SYNOPSIS

fetchmail [option...] [mailserver...]
fetchmailconf

 

DESCRIPTION

fetchmail is a mail-retrieval and forwarding utility; it fetchesmail from remote mail servers and forwards it to your local (client)machine's delivery system. You can then handle the retrieved mail usingnormal mail user agents such as mutt(1), elm(1) orMail(1). The fetchmail utility can be run in a daemon modeto repeatedly poll one or more systems at a specified interval.

The fetchmail program can gather mail from servers supporting anyof the common mail-retrieval protocols: POP3, IMAP2bis, IMAP4, and IMAP4rev1.It can also use the ESMTP ETRN extension and ODMR. (The RFCs describing allthese protocols are listed at the end of this manual page.)

While fetchmail is primarily intended to be used over on-demandTCP/IP links (such as SLIP or PPP connections), it may also be useful asa message transfer agent for sites which refuse for security reasons topermit (sender-initiated) SMTP transactions with sendmail.

 

DEPRECATION AND CRYPTOGRAPHIC SECURITY WARNINGS

Several cryptographic algorithms that are referenced by mail standaredsfor authentication were based on MD4 or MD5 or SHA1 algorithms that weredeveloped in 1990, 1991 and 1995 respectively.30 years later, these are no longer deemed secure, and are considered broken.

Not all IETF standards and RFCs have given up on them, and some protocolsactively require something that incorporates MD4, MD5 or SHA1 in some formso disabling their use in fetchmail altogether would also pull the plugon, say, protocols such as ODMR, or formerly-popular authentication schemessuch as POP3 with APOP.

The recommendation is to prefer TLS-wrapped connections via dedicatedports 993 (IMAP4) or 995 (POP3) or STARTTLS in-band negotiation withsuch authentication schemes, to reduce the risk to expose login credentials.

Also, weak authentication schemes will be phased out from future fetchmailreleases, please see the NEWS file that should have come with your distributionof fetchmail.

 

SUPPORT, TROUBLESHOOTING

For troubleshooting, tracing and debugging, you need to increasefetchmail's verbosity to actually see what happens. To do that, pleaserun both of the two following commands,adding all of the options you'd normally use.

env LC_ALL=C fetchmail -V -v --nodetach --nosyslog

(This command line prints in English how fetchmail understands yourconfiguration.)

env LC_ALL=C fetchmail -vvv  --nodetach --nosyslog

(This command line actually runs fetchmail with verbose English output.)

Also seeitem #G3 in fetchmail's FAQ

You can omit the LC_ALL=C part above if you want output in the locallanguage (if supported). However if you are posting to mailing lists,please leave it in. The maintainers do not necessarily understand yourlanguage, please use English.

 

QUICKSTART

1. Set up a local SMTP mail server, or command-line based mail delivery agentsuch as maildrop or dovecot-lda, configure and test and debug it. Make surethat mail you deliver to yourself through it ends up in the right place.Do NOT continue unless and until this works or you risk losing mail!

2. Create a .fetchmailrc file in your home directory that looksroughly like this, for POP3 fetches.

poll mailserver.example.org proto POP3 uidluser joe.sixpackkeep ssl

You need to adjust several elements here:mailserver.example.org is the server's name. joe.sixpack is the login nameto use for the server.keep states that messages should be left on the server, rather than deleted.ssl states that the connection should be encrypted.If you need to use IMAP instead of POP3,change "proto POP3 uidl" to "proto IMAP".

If you chose to deliver through a command-line program, add an mda option,for instance:

mda "/usr/bin/maildrop -d %T"

3. And then make sure the ~/.fetchmailrc file is not readable or writableto anyone but yourself:

chmod 0600 ~/.fetchmailrc

4. Finally, run fetchmail in verbose mode and see that it works.To limit impact, if something goes wrong, we just try two messages:

fetchmail -v --fetchlimit 2

If then the POP3 server refuses UIDL, you cannot use the "keep" optionon that server and you need to remove the uidl and keep options, but notethat then fetchmail will remove messages it has successfullydelivered from the server.

 

TLS (SSL) QUICKSTART

Your fetchmail distribution should have come with a README.SSL file, which see.It is recommended to configure all polls with --sslmode wrapped orif supported by the server, else --sslmode starttls, which configures fetchmailalong recent IETF proposed standards and best current practices, RFC-8314,RFC-8996, RFC-8997.

Fetchmail 6.6.0 and newer also support TLS and STARTTLS for SMTP,see the --smtphost option for how to configure those.

 

CONCEPTS

If fetchmail is used with a POP or an IMAP server (but not withETRN or ODMR), it has two fundamental modes of operation for each useraccount from which it retrieves mail: singledrop- andmultidrop-mode.

In singledrop-mode,

fetchmail assumes that all messages in the user's account(mailbox) are intended for a single recipient. The identity of therecipient will either default to the local user currently executingfetchmail, or will need to be explicitly specified in theconfiguration file.

fetchmail uses singledrop-mode when the fetchmailrc configurationcontains at most a single local user specification for a given serveraccount.

In multidrop-mode,

fetchmail assumes that the mail server account actually containsmail intended for any number of different recipients. Therefore,fetchmail must attempt to deduce the proper "envelope recipient"from the mail headers of each message. In this mode of operation,fetchmail almost resembles a mail transfer agent (MTA).

Note that neither the POP nor IMAP protocols were intended for use inthis fashion, and hence envelope information is often not directlyavailable. The ISP must store the envelope information in some messageheader and. The ISP must also store one copy of the message perrecipient. If either of the conditions is not fulfilled, this process isunreliable, because fetchmail must then resort to guessing thetrue envelope recipient(s) of a message. This usually fails for mailinglist messages and Bcc:d mail, or mail for multiple recipients in yourdomain.

fetchmail uses multidrop-mode when more than one local user and/ora wildcard is specified for a particular server account in theconfiguration file.

In ETRN and ODMR modes,

these considerations do not apply, as these protocols are based on SMTP,which provides explicit envelope recipient information. These protocolsalways support multiple recipients.

As each message is retrieved, fetchmail normally delivers it viaSMTP to port 25 on the machine it is running on (localhost), just asthough it were being passed in over a normal TCP/IP link.fetchmail provides the SMTP server with an envelope recipientderived in the manner described previously. The mail will then bedelivered according to your MTA's rules (the Mail Transfer Agent isusually sendmail(8), exim(8), or postfix(8)).Invoking your system's MDA (Mail Delivery Agent) is the duty of yourMTA. All the delivery-control mechanisms (such as .forward files)normally available through your system MTA and local delivery agentswill therefore be applied as usual.

If your fetchmail configuration sets a local MDA (see the --mdaoption), it will be used directly instead of talking SMTP to port 25.

If the program fetchmailconf is available, it will assist you insetting up and editing a fetchmailrc configuration. It runs under the Xwindow system and requires that the language Python and the Tk toolkit(with Python bindings) be present on your system. If you are firstsetting up fetchmail for single-user mode, it is recommended that youuse Novice mode. Expert mode provides complete control of fetchmailconfiguration, including the multidrop features. In either case,the 'Autoprobe' button will tell you the most capable protocol a givenmail server supports, and warn you of potential problems with thatserver.

 

PREFACE ON THIS MANUAL

Fetchmail's run-time strings have been translated (localized) to somelanguages, but the manual is only available in English. In somesituations, for comparing output to manual, it may be helpful toswitch fetchmail to English output by overriding the locale variables,for instance:

env LC_ALL=C fetchmail # add other options before the hash

env LANG=en fetchmail # other options before the hash

or similar. Details vary by operating system.

 

GENERAL OPERATION

The behavior of fetchmail is controlled by command-line options and arun control file, ~/.fetchmailrc,the syntax of which we describe in a later section (this file is whatthe fetchmailconf program edits). Command-line options override~/.fetchmailrc declarations.

Each server name that you specify following the options on the commandline will be queried. If you do not specify any servers on the commandline, each 'poll' entry in your ~/.fetchmailrc file will bequeried, unless the idle option is used, which see.

To facilitate the use of fetchmail in scripts and pipelines, itreturns an appropriate exit code upon termination -- see EXIT CODESbelow.

The following options modify the behavior of fetchmail. It isseldom necessary to specify any of these once you have aworking .fetchmailrc file set up.

Almost all options have a corresponding keyword which can be used todeclare them in a .fetchmailrc file.

Some special options are not covered here, but are documented insteadin sections on AUTHENTICATION and DAEMON MODE which follow. 

General Options

-? | --help

Displays option help.

-V | --version

Displays the version information for your copy of fetchmail. No mailfetch is performed. Instead, for each server specified, all the optioninformation that would be computed if fetchmail were connecting to thatserver is displayed. Any non-printable characters in passwords or other stringnames are shown as back-slashed C-like escape sequences. This option is usefulfor verifying that your options are set the way you want them.

-c | --check

Return a status code to indicate whether there is mail waiting,without actually fetching or deleting mail (see EXIT CODES below).This option turns off daemon mode (in which it would be useless). Itdoes not play well with queries to multiple sites, and does not workwith ETRN or ODMR. It will return a false positive if you leave read butundeleted mail in your server mailbox and your fetch protocol cannottell kept messages from new ones. This means it will work with IMAP,and may occasionally flake out under POP3.

-s | --silent

Silent mode. Suppresses all progress/status messages that arenormally echoed to standard output during a fetch (but does notsuppress actual error messages). The --verbose option overrides this.

-v | --verbose

Verbose mode. All control messages passed between fetchmailand the mail server are echoed to stdout. Overrides --silent.Doubling this option (-v -v) causes extra diagnostic informationto be printed.

--nosoftbounce

(since v6.3.10, Keyword: set no softbounce, since v6.3.10)
Hard bounce mode. All permanent delivery errors cause messages to bedeleted from the upstream server, see "no softbounce" below.

--softbounce

(since v6.3.10, Keyword: set softbounce, since v6.3.10)
Soft bounce mode. All permanent delivery errors cause messages to beleft on the upstream server if the protocol supports that.This option is on by default to match historic fetchmail documentation,and will be changed to hard bounce mode in the next fetchmail release.

 

Disposal Options

-a | --all | (since v6.3.3) --fetchall

(Keyword: fetchall, since v3.0)
Retrieve both old (seen) and new messages from the mail server. Thedefault is to fetch only messages the server has not marked seen.Under POP3, this option also forces the use of RETR rather than TOP.While the -a and --all command-line and fetchall rcfile options have beensupported for a long time, the --fetchall command-line option was added inv6.3.3.

-k | --keep

(Keyword: keep)
Keep retrieved messages on the remote mail server. Normally, messagesare deleted from the folder on the mail server after they have been retrieved.Specifying the keep option causes retrieved messages to remain inyour folder on the mailserver. This option does not work with ETRN orODMR.

-K | --nokeep

(Keyword: nokeep)
Delete retrieved messages from the remote mail server. Thisoption forces retrieved mail to be deleted. It may be useful ifyou have specified a default of keep in your.fetchmailrc. This option is forced on with ETRN and ODMR.

--moveto <folder>

(Keyword: moveto)
In IMAP mode, instead of flushing a message, move it to the given IMAP folderinstead. This is useful for avoiding data loss while testing, and is thepreferred way to delete emails on certain implementations, for example Googlewants you to delete mails by moving them to [Gmail]/Trash. Only available forIMAP servers. This option is only accepted with --proto imap, but notif IMAP is chosen automatically. It is ineffective when --keep isin effect.

-F | --flush

(Keyword: flush)
POP3/IMAP only. This is a dangerous option and can cause mail loss whenused improperly. It deletes old (seen) messages from the mail serverbefore retrieving new messages. Warning: This can cause mail loss ifyou check your mail with other clients than fetchmail, and causefetchmail to delete a message it had never fetched before. It can alsocause mail loss if the mail server marks the message seen afterretrieval (IMAP2 servers). You should probably not use this option in yourconfiguration file. What you probably want is the default setting: if you do notspecify '-k', then fetchmail will automatically delete messages aftersuccessful delivery.

--limitflush

POP3/IMAP only, since version 6.3.0. Delete oversized messages from themail server before retrieving new messages. The size limit should beseparately specified with the --limit option. This option does notwork with ETRN or ODMR.

 

Protocol and Query Options

-p <proto> | --proto <proto> | --protocol <proto>

(Keyword: proto[col])
Specify the protocol to use when communicating with the remotemail server. If no protocol is specified, the default is AUTO.proto may be one of the following:

AUTO

Tries IMAP and POP3 (skipping any of these for which supporthas not been compiled in).

POP3

Post Office Protocol 3

KPOP

Use POP3 with Kerberos V5 authentication on port 1109.

IMAP

IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail automatically detects theircapabilities).

ETRN

Use the ESMTP ETRN option.

ODMR

Use the On-Demand Mail Relay ESMTP profile.

All these alternatives work in basically the same way (communicatingwith standard server daemons to fetch mail already delivered to amailbox on the server) except ETRN and ODMR. The ETRN modeallows you to ask a compliant ESMTP server (such as BSD sendmail atrelease 8.8.0 or higher) to immediately open a sender-SMTP connectionto your client machine and begin forwarding any items addressed toyour client machine in the server's queue of undelivered mail. TheODMR mode requires an ODMR-capable server and works similarly toETRN, except that it does not require the client machine to havea static DNS.

--idle (since 6.3.3)

(Keyword: idle, since before 6.0.0)
Enable IDLE use (effective only with IMAP). Note that this works withonly one account and one folder at a given time, other folders oraccounts will not be polled when idle is in effect! While the idle rcfilekeyword had been supported for a long time, the --idle command-lineoption was added in version 6.3.3. IDLE use means that fetchmail tellsthe IMAP server to send notice of new messages, so they can be retrievedsooner than would be possible with regular polls.Fetchmail also contains a workaround to emulate IDLE; this workaround wasineffective since 6.4.22 and fixed in 6.5.3 (broken by commit 616e8c70and repaired in f91923b5), Gitlab issue #69.

--forceidle (since 6.5.0)

(Keyword: forceidle, since 6.5.0)
Use IDLE even if the server does not advertise it in its capabilities. Thisis a dangerous option, use carefully.

--idletimeout (since 6.5.0)

(Keyword: idletimeout, since 6.5.0)
Set the timeout (in seconds) for the IDLE command because too many serversbreak the protocol (which requires 30 minutes) and hang up after a fewminutes. Default value: 1680 s (= 28 min).

-P <portnumber> | --service <servicename>

(Keyword: service) Since version 6.3.0.
The service option permits you to specify a service name to connect to.You can specify a decimal port number here, if your services databaselacks the required service-port assignments. See the FAQ item R12 andthe --ssl documentation for details. This replaces the older --portoption.

Note that this does not magically switch between TLS-wrapped and STARTTLSmodes, if you specify a port number or service name here that is TLS-wrapped,meaning it starts to negotiate TLS before sending application data in the clear,you may need to specify --ssl on the command line or ssl in your rcfile.

--port <portnumber>

(Keyword: port)
Obsolete version of --service that does not take service names.Note: this option may be removed from a future version.

--principal <principal>

(Keyword: principal)
The principal option permits you to specify a service principal formutual authentication. This is applicable to POP3 or IMAP with Kerberos4 authentication only. It does not apply to Kerberos 5 or GSSAPI. Thisoption may be removed in a future fetchmail version.

-t <seconds> | --timeout <seconds>

(Keyword: timeout)
The timeout option allows you to set a server-non-responsetimeout in seconds. If a mail server does not send a greeting messageor respond to commands for the given number of seconds,fetchmail will drop the connection to it. Without such a timeoutfetchmail might hang until the TCP connection times out, trying to fetchmail from a down host, which may be very long.This would be particularly annoying for a fetchmail running in thebackground. There is a default timeout which fetchmail~-V will report. If agiven connection receives too many timeouts in succession, fetchmail willconsider it wedged and stop retrying. The calling user will be notified byemail if this happens.

Beginning with fetchmail 6.3.10, the SMTP client uses the recommended minimumtimeouts from RFC-5321 while waiting for the SMTP/LMTP server it is talking to.You can raise the timeouts even more, but you cannot shorten them. This is toavoid a painful situation where fetchmail has been configured with a shorttimeout (a minute or less), ships a long message (many MBytes) to the localMTA, which then takes longer than timeout to respond "OK", which it eventuallywill; that would mean the mail gets delivered properly, but fetchmail cannotnotice it and will thus re-fetch this big message over and over again.

--plugin <command>

(Keyword: plugin)
The plugin option allows you to use an external program to establish the TCPconnection. This is useful if you want to use ssh, or need some specialfirewall setup. The program will be looked up in $PATH and can optionallybe passed the host name and port as arguments using "%h" and "%p" respectively(note that the interpolation logic is rather primitive, and these tokens mustbe bounded by whitespace or beginning of string or end of string).Fetchmail will write to the plugin's stdin and read from the plugin'sstdout.

--plugout <command>

(Keyword: plugout)
Identical to the plugin option above, but this one is used for the SMTPconnections.

-r <name> | --folder <name>

(Keyword: folder[s])
Causes a specified non-default mail folder on the mail server (orcomma-separated list of folders) to be retrieved. The syntax of thefolder name is server-dependent. This option is not available underPOP3, ETRN, or ODMR.

--tracepolls

(Keyword: tracepolls)
Tell fetchmail to poll trace information in the form 'pollingaccount %s' and 'folder %s' to the Received line it generates,where the %s parts are replaced by the user's remote name, the polllabel, and the folder (mailbox) where available (the Received headeralso normally includes the server's true name). This can be used tofacilitate mail filtering based on the account it is being receivedfrom. The folder information is written only since version 6.3.4.

--ssl

(Keyword: ssl, obsolescent in 7.0.0)
This option is obsolete as of 7.0.0 and should be replaced by--sslmode wrapped (or sslmode wrapped in the rcfile).

--nossl

(Keyword: nossl)
Cancels out a default of ssl given earlier, in defaults, or in an rcfileif --nossl is given on the command-line. Use --sslproto with properargument to enable STARTTLS.

--sslcert <name>

(Keyword: sslcert)
For certificate-based client authentication. Some SSL encrypted serversrequire client side keys and certificates for authentication. In mostcases, this is optional. This specifies the location of the public keycertificate to be presented to the server at the time the SSL session isestablished. It is not required (but may be provided) if the serverdoes not require it. It may be the same file as the private key(combined key and certificate file) but this is not recommended. Alsosee --sslkey below.

NOTE: If you use client authentication, the user name is fetchedfrom the certificate's CommonName and overrides the name set with--user.

--sslkey <name>

(Keyword: sslkey)
Specifies the file name of the client side private SSL key. Some SSLencrypted servers require client side keys and certificates forauthentication. In most cases, this is optional. This specifiesthe location of the private key used to sign transactions with the serverat the time the SSL session is established. It is not required (but maybe provided) if the server does not require it. It may be the same fileas the public key (combined key and certificate file) but this is notrecommended.

If a password is required to unlock the key, it will be prompted for atthe time just prior to establishing the session to the server. This cancause some complications in daemon mode.

Also see --sslcert above.

--sslmode {none|wrapped|starttls=may|starttls=must}

(Keyword: sslmode, new in 7.0.0)
Sets the encryption state of the connection. starttls=may is thedefault. Meanings are:

none

A cleartext connection is used. This may expose login credentials suchas passwords.

wrapped

A legacy SSL/TLS-wrapped connection on a separate, dedicated port (995for POP3 and 993 for IMAP) is used. Fetchmail versions up to 6.X.Ycalled this --ssl. The SSL negotiation starts right away, before anyprotocol conversation.

starttls=may

Fetchmail probes whether the server offers the STARTTLS extension, andif it does, upgrades to an encrypted channel. Connections are made tothe default base protocol ports by default, and the protocol exchangestarts with capability/extension negotiation before the SSL/TLS upgradecauses the remainder of the session to be encrypted.

NOTEthat with sslcertck enabled (also default), this option is implicityupgraded to starttls=must, described below:

starttls=must

Fetchmail connects to the base protocol port and upgrades to anencrypted connection in-band (via STARTTLS). If the STARTTLS negotiationfails, fetchmail aborts the connection.

--sslprotocolversion <name>

(Keyword: sslprotocolversion, new in 7.0.0)
NOTEthat this option has different semantics from the removed --sslprotooption of fetchmail v6.x.y and older. For selecting whether and how toencrypt a connection, see the --sslmode option.

NOTEthat this option, in the new form, is hardly ever necessary, and onlyuseful with buggy SSL/TLS implementations on servers, which areextremely rare.

This option determines how fetchmail selects the SSL/TLS protocol version.Recognized values for --sslprotocolversion are given below.You should normally choose one of the auto-negotiating options,i. e. 'tls1.2+' or 'auto' or one of the otheroptions ending in a plus (+) character.Note that depending on OpenSSL library version and configuration, some optionscause run-time errors because the requested SSL or TLS versions are notsupported by the particular installed OpenSSL library. Test well before youdeploy for unattended operation.

'auto'

(default, the same as TLS1.2+). Since v6.4.0, changed in v6.5.0. Require TLS.Auto-negotiate TLSv1.2 or newer, disable downgrade below.Fetchmail has not supported SSLv2 since v6.4.0 andhas not supported SSLv3 since v6.5.0.(fetchmail versions older than v6.5.0 have auto-negotiated older protocols,v6.4.x would permit TLSv1.0 by default, v6.3.x would permit SSLv3).

'', the empty string

XXX FIXME - update and check behavior:Disable STARTTLS. If --ssl is given for the same server, log an errorand pretend that 'auto' had been used instead.

'SSL23'

see 'auto'. Deprecated, recognized for backwards compatibility.

'TLS'

see 'auto'. For symmetry with OpenSSL client method names.

'TLS1'

Require TLSv1. This does not negotiate TLSv1.1 or newer, and isdiscouraged. Replace by TLS1+ unless the latter chokes your server.

'TLS1+'

Since v6.4.0. This is an auto-negotiation feature that willpermit TLSv1.0 and newer.

'TLS1.1'

Require TLS v1.1 exactly.

'TLS1.1+'

Require TLS. Auto-negotiate TLSv1.1 or newer.

'TLS1.2'

Require TLS v1.2 exactly.

'TLS1.2+'

Since v6.4.0. Require TLS. Auto-negotiate TLSv1.2 or newer.This is the default in fetchmail v6.5.x.

'TLS1.3'

Require TLS v1.3 exactly.

'TLS1.3+'

Require TLS. Auto-negotiate TLSv1.3 or newer.

--sslcertck

(Keyword: sslcertck, default enabled since v6.4.0)
--sslcertck causes fetchmail to require that SSL/TLS be used anddisconnect unless it can successfully negotiate SSL or TLS, or if itcannot successfully verify and validate the certificate and follow it toa trust anchor (or trusted root certificate). The trust anchors aregiven as a set of local trusted certificates (see the sslcertfileand sslcertpath options). If the server certificate cannot beobtained or is not signed by one of the trusted ones (directly orindirectly), fetchmail will disconnect, regardless of thesslfingerprint option.

--nosslcertck

(Keyword: no sslcertck, only in v6.4.X)
The opposite of --sslcertck, this is a discouraged option. It permitsfetchmail to continue connecting even if the server certificate failedthe verification checks. Should only be used together with--sslfingerprint.

--sslcertfile <file>

(Keyword: sslcertfile, since v6.3.17)
Sets the file fetchmail uses to look up local certificates. The default isempty. This can be given in addition to --sslcertpath below, andcertificates specified in --sslcertfile will be processed before thosein --sslcertpath. The option can be used in addition to--sslcertpath.

The file is a text file. It contains the concatenation of trusted CAcertificates in PEM format.

Note that using this option will suppress loading the default SSL trusted CAcertificates file unless you set the environment variableFETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.

--sslcertpath <directory>

(Keyword: sslcertpath)
Sets the directory fetchmail uses to look up local certificates. The default isyour OpenSSL default directory. The directory must be hashed the way OpenSSLexpects it - every time you add or modify a certificate in the directory, youneed to use the c_rehash tool (which comes with OpenSSL in the tools/sub-directory). Also, after OpenSSL upgrades, you may need to runc_rehash.

This can be given in addition to --sslcertfile above, which see forprecedence rules.

Note that using this option will suppress adding the default SSL trusted CAcertificates directory unless you set the environment variableFETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty value.

--sslcommonname <common name>

(Keyword: sslcommonname; since v6.3.9)
Use of this option is discouraged. Before using it, contact theadministrator of your upstream server and ask for a proper SSLcertificate to be used. If that cannot be attained, this option can beused to specify the name (CommonName) that fetchmail expects on theserver certificate. A correctly configured server will have this set tothe host name by which it is reached, and by default fetchmail willexpect as much. Use this option when the CommonName is set to some othervalue, to avoid the "Server CommonName mismatch" warning, and only ifthe upstream server's operator cannot be made to use proper certificates.

--sslfingerprint [{<algo>}]<fingerprint>

(Keyword: sslfingerprint)
Specify the fingerprint of the server key inhexadecimal notation with colons separating groups of two digits.This is the format that fetchmail uses to report the fingerprintwhen an SSL connection is established.When this is specified, fetchmail will compare the server keyfingerprint with the given one, and the connection will fail if they do notmatch, regardless of the sslcertck setting. The connection willalso fail if fetchmail cannot obtain an SSL certificate from the server.This can be used to prevent man-in-the-middle attacks, but the fingerprint from the server must be obtained or verified over a securechannel, and certainly not over the same Internet connection thatfetchmail would use.

The fingerprint can be prefixed with an EVP_MD digest algorithm name in curlybraces, for instance, {MD5}00:01:...:0F.All digest algorithms that your SSL provider library supports can be used.Choose a sensible one, for instance, SHA256.If the {algo} prefix is omitted, MD5 is used for compatibility with fetchmail6.4 and older.

Using this option will prevent printing certificate verification errorsas long as --nosslcertck is in effect.

If you just want the --verbose log output to switch logging to a different hash,without pinning the server's certificate hash, you canuse --sslfingerprint '{algo}*', f.i., --sslfingerprint '{SHA256}*'

To obtain the fingerprint of a certificate stored in the file cert.pem,try:

        openssl x509 -in cert.pem -noout -sha256 -fingerprint

For details, seex509(1ssl).

 

Delivery Control Options

-S <hosts> | --smtphost <hosts>

(Keyword: smtp[host])
(since v6.6.0, fetchmail supports TLS and STARTTLS for SMTP hosts)
(since v6.5.6, fetchmail knows how to generate RFC-5321 IP address literalsfrom a bare numeric-address IPv4 or IPv6 string)

Specify a hunt list of hosts to forward mail to (one or morehost names, comma-separated). Hosts are tried in list order; the firstone that is up becomes the forwarding target for the current run. Ifthis option is not specified, 'localhost' is used as the default.Each host name may have a port number following the host name. Theport number is separated from the host name by a slash; the defaultport is "smtp". If you specify an absolute path name (beginning witha /), it will be interpreted as the name of a UNIX socket acceptingLMTP connections (such as is supported by the Cyrus IMAP daemon).
Example:

--smtphost server1,server2/2525,server3,/var/imap/socket/lmtp

This option can be used with ODMR, and will make fetchmail a relaybetween the ODMR server and SMTP or LMTP receiver.

Each host name for SMTP servers supports up to four options separated witha slash (/):

/25 or /587 or /smtp or /465 or /smtps

25 or any other number between 1 and 65535 designates the port number to connect to;smtp or any other service name that the system can resolve (simple setups may use /etc/services);if not given, fetchmail will use default port numbers as described below.

One of

/notls

disables opportunistic STARTTLS even if offered by the server. This is impliedif the hostname islocalhostexactly.

/starttls

requires the server to offer STARTTLS in the Extended Hello (EHLO) and requiresthat the server certificate validates as if --sslcertck had been set.The default port will be 25.

/tls

negotiates TLS wrapping before exchanging the greeting and requires that theserver certificate validates as if --sslcertck had been set.The default port will be 465.

None of /notls, /tls, /starttls:

opportunistic TLS (except for localhost, see above).Will try to negotiate STARTTLS if offered by the server, but will not insiston certificate validation, as if by --nosslcertck.

/tlsproto=PROTO

behaves as though --sslproto PROTO had been given, which see.Ignored if /notls is active.

/servername=NAME

switches the expected X.509 certificate name to NAME and will pass it throughServer Name Indication (SNI) if the SMTP service multiplexes by server name.Ignored if /notls is active.

NOTE 1: any text not recognized explicitly will be considered a service name;syntax errors such as mistyped options can show up as confusinggetaddrinfo() errors to resolve a service, for instance, as 'Servname notsupported for ai_socktype'.

NOTE 2: when contradictory options are given, the last one given prevails

Example:

--smtphost dnsname.example.org/25/starttls/tlsproto=tls1.3/servername=commonname.example.com

would resolve dnsname.example.org, connect to it on port 25, try to issuean STARTTLS command and upgrade to TLS v1.3 and expect that the server'sX.509 certificate matches the name commonname.example.com.

WARNING for versions 6.5.5 and before:if you use address numeric IP addresses here, be sure touse --smtpaddress or --smtpname (either of which see) with a validSMTP address literal!

--esmtpname <authid>

(since v6.5.7; Keyword: esmtpname, since v5.9.9)Sets the authorization ID for SMTP AUTH to be used for logging into the SMTPserver. Defaults to fetchmail's notion of the running user, taken from thefirst defined environment variable FETCHMAILUSER, LOGNAME, USER.(not currently listed in --help output)

NOTE: This is per "poll" and will be the same for all servers listed inyour smtphost list!

NOTE: fetchmail does not currently enforce that the connection goes vialoopback interface or TLS secured encrypted layer - be sure to enforce TLS or STARTTLS on theSMTP server if it's not your localhost.

--esmtppassword <secret>

(since v6.5.7; Keyword: esmtppassword, since v5.9.9)Sets the secret/password for SMTP AUTH to be used for logging into the SMTP server.(not currently listed in --help output)

NOTE 1: instead of in fetchmail's rcfile, you can put the password into thewhich see.

NOTE 2: This is per "poll" and will be the same for all servers listed inyour smtphost list! The password will be taken for the first smtphost, or it's /servername=option in the list that does have a .netrc entry.

NOTE 3: fetchmail does not currently enforce that the connection goes vialoopback interface or TLS secured encrypted layer - be sure to enforce TLS or STARTTLS on theSMTP server if it's not your localhost.

--fetchdomains <hosts>

(Keyword: fetchdomains)
In ETRN or ODMR mode, this option specifies the list of domains theserver should ship mail for once the connection is turned around. Thedefault is the FQDN of the machine running fetchmail.

-D <domain> | --smtpaddress <domain>

(Keyword: smtpaddress)
Specify the domain to be appended to addresses in RCPT TO lines shippedto SMTP. When this is not specified, the name of the SMTP server (asspecified by --smtphost) is used for SMTP/LMTP and 'localhost' is usedfor UNIX socket/BSMTP.

NOTE: if you intend to use numeric addresses with fetchmail 6.5.5 or older,or so-called address literals per the SMTP standard, write them in properSMTP syntax, for instance --smtpaddress "[192.0.2.6]"or --smtpaddress "[IPv6:2001:DB8::6]".

--smtpname <userAATTdomain>

(Keyword: smtpname)
Specify the user and domain to be put in RCPT TO lines shipped to SMTP.The default user is the current local user. Please also see the NOTEabout --smtpaddress and address literals above.

-Z <nnn> | --antispam <nnn[, nnn]...>

(Keyword: antispam)
Specifies the list of numeric SMTP errors that are to be interpretedas a spam-block response from the listener. A value of -1 disablesthis option. For the command-line option, the list values shouldbe comma-separated. Note that the antispam values only apply to "MAILFROM" responses in the SMTP dialogue, but several MTAs (Postfix inits default configuration, qmail) defer the anti-spam response codeuntil after the RCPT TO. --antispam does not work in thesecircumstances. Also see --softbounce (default) and its inverse.

-m <command> | --mda <command>

(Keyword: mda)
This option lets fetchmail use a Message or Local Delivery Agent(MDA or LDA) directly, rather than forward via SMTP or LMTP.

To avoid losing mail, use this option only with MDAs like maildrop orMTAs like sendmail that exit with a nonzero status on disk-full and otherdelivery errors; the nonzero status tells fetchmail that delivery failedand prevents the message from being deleted on the server.

If fetchmail is running as root, it sets its user id whiledelivering mail through an MDA as follows: First, the FETCHMAILUSER,LOGNAME, and USER environment variables are checked in this order. Thevalue of the first variable from his list that is defined (even if it isempty!) is looked up in the system user database. If none of thevariables is defined, fetchmail will use the real user id it was startedwith. If one of the variables was defined, but the user stated thereis not found, fetchmail continues running as root, without checkingremaining variables on the list. Practically, this means that if yourun fetchmail as root (not recommended), it is most useful to define theFETCHMAILUSER environment variable to set the user that the MDA shouldrun as. Some MDAs (such as maildrop) are designed to be setuid root andsetuid to the recipient's user id, so you do not lose functionality thisway even when running fetchmail as unprivileged user. Check the MDA'smanual for details.

Some possible MDAs are "/usr/sbin/sendmail -i -f %F -- %T"(Note:some several older or vendor sendmail versions mistake -- for anaddress, rather than an indicator to mark the end of the option arguments),"/usr/bin/deliver" and "/usr/bin/maildrop -d %T". Local deliveryaddresses will be inserted into the MDA command wherever you place a%T; the mail message's From address will be inserted where you placean %F.

Do NOT enclose the %F or %T string in single quotes!For both %T and %F, fetchmail encloses the addresses in single quotes('), after removing any single quotes they may contain, before the MDAcommand is passed to the shell.

Do NOT use an MDA invocation that dispatches on the contents ofTo/Cc/Bcc, like "sendmail -i -t" or "qmail-inject", it will createmail loops and bring the just wrath of many postmasters down upon yourhead. This is one of the most frequent configuration errors!

Also, do not try to combine multidrop mode with an MDA suchas maildrop that can only accept one address, unless your upstreamstores one copy of the message per recipient and transports the enveloperecipient in a header; you will lose mail.

The well-knownprocmail(1)package is very hard to configure properly, it has a very nasty "fallthrough to the next rule" behavior on delivery errors (even temporaryones, such as out of disk space if another user's mail daemon copies themailbox around to purge old messages), so your mail will end up in thewrong mailbox sooner or later. The proper procmail configuration isoutside the scope of this document. Usingmaildrop(1)is usually much easier, and many users find the filter syntax used bymaildrop easier to understand.

Finally, we strongly advise that you do not use qmail-inject. Thecommand line interface is non-standard without providing benefits fortypical use, and fetchmail makes no attempts to accommodateqmail-inject's deviations from the standard. Some of qmail-inject'scommand-line and environment options are actually dangerous and cancause broken threads, non-detected duplicate messages and forwardingloops.

--lmtp

(Keyword: lmtp)
Cause delivery via LMTP (Local Mail Transfer Protocol). A servicehost and port must be explicitly specified on each host in thesmtphost hunt list (see above) if this option is selected; the defaultport 25 will (in accordance with RFC 2033) not be accepted.

--bsmtp <filename>

(Keyword: bsmtp)
Append fetched mail to a BSMTP file. This simply contains the SMTPcommands that would normally be generated by fetchmail when passingmail to an SMTP listener daemon.

An argument of '-' causes the SMTP batch to be written to standardoutput, which is of limited use: this only makes sense for debugging,because fetchmail's regular output is interspersed on the same channel,so this is not suitable for mail delivery. This special mode may beremoved in a later release.

Note that fetchmail's reconstruction of MAIL FROM and RCPT TO lines isnot guaranteed correct; the caveats discussed under THE USE AND ABUSE OFMULTIDROP MAILBOXES below apply. This mode has precedence before--mda and SMTP/LMTP.

--bad-header {reject|accept}

(Keyword: bad-header; since v6.3.15)
Specify how fetchmail is supposed to treat messages with bad headers,i.e., headers with bad syntax. Traditionally, fetchmail has rejected suchmessages, but some distributors modified fetchmail to accept them. You can nowconfigure fetchmail's behaviour per server.

--retrieve-error {abort|continue|markseen}

(Keyword: retrieve-error; since v7.0)
Specify how fetchmail is supposed to treat messages which fail to beretrieved due to server errors, i. e. fetching the message body fails witha server error. Traditionally, fetchmail has aborted the session leavingboth the message with the error and any subsequent messages on the server.Both the continue and markseen options will allow the session to continueenabling subsequent messages on the server to be retrieved. You can nowconfigure fetchmail's behaviour per server.

 

Resource Limit Control Options

-l <maxbytes> | --limit <maxbytes>

(Keyword: limit)
Takes a maximum octet size argument, where 0 is thedefault and also the special value designating "no limit".If nonzero, messages larger than this size will not be fetched and willbe left on the server (in foreground sessions, the progress messageswill note that they are "oversized"). If the fetch protocol permits (inparticular, under IMAP or POP3 without the fetchall option) the messagewill not be marked seen.

An explicit --limit of 0 overrides any limits set in yourrun control file. This option is intended for those needing tostrictly control fetch time due to expensive and variable phone rates.

Combined with --limitflush, it can be used to delete oversizedmessages waiting on a server. In daemon mode, oversize notificationsare mailed to the calling user (see the --warnings option). Thisoption does not work with ETRN or ODMR.

-w <interval> | --warnings <interval>

(Keyword: warnings)
Takes an interval in seconds. When you call fetchmailwith a 'limit' option in daemon mode, this controls the interval atwhich warnings about oversized messages are mailed to the calling user(or the user specified by the 'postmaster' option). One suchnotification is always mailed at the end of the first poll thatthe oversized message is detected. Thereafter, re-notification issuppressed until after the warning interval elapses (it will takeplace at the end of the first following poll).

-b <count> | --batchlimit <count>

(Keyword: batchlimit)
Specify the maximum number of messages that will be shipped to an SMTPlistener before the connection is deliberately torn down and rebuilt(defaults to 0, meaning no limit). An explicit --batchlimit of 0overrides any limits set in your run control file. Whilesendmail(8) normally initiates delivery of a message immediatelyafter receiving the message terminator, some SMTP listeners are not soprompt. MTAs like smail(8) may wait till thedelivery socket is shut down to deliver. This may produce annoyingdelays when fetchmail is processing very large batches. Settingthe batch limit to some nonzero size will prevent these delays. Thisoption does not work with ETRN or ODMR.

-B <number> | --fetchlimit <number>

(Keyword: fetchlimit)
Limit the number of messages accepted from a given server in a singlepoll. By default there is no limit. An explicit --fetchlimit of 0overrides any limits set in your run control file.This option does not work with ETRN or ODMR.

--fetchsizelimit <number>

(Keyword: fetchsizelimit)
Limit the number of sizes of messages accepted from a given server ina single transaction. This option is useful in reducing the delay indownloading the first mail when there are too many mails in themailbox. By default, the limit is 100. If set to 0, sizes of allmessages are downloaded at the start.This option does not work with ETRN or ODMR. For POP3, the only validnon-zero value is 1.

--fastuidl <number>

(Keyword: fastuidl)
Do a binary instead of linear search for the first unseen UID. Binarysearch avoids downloading the UIDs of all mails. This saves time(especially in daemon mode) where downloading the same set of UIDs ineach poll is a waste of bandwidth. The number 'n' indicates how rarelya linear search should be done. In daemon mode, linear search is usedonce followed by binary searches in 'n-1' polls if 'n' is greater than1; binary search is always used if 'n' is 1; linear search is alwaysused if 'n' is 0. In non-daemon mode, binary search is used if 'n' is1; otherwise linear search is used. The default value of 'n' is 4.This option works with POP3 only.

-e <count> | --expunge <count>

(Keyword: expunge)
Arrange for deletions to be made final after a given number ofmessages. Under POP3, fetchmail cannot make deletions finalwithout sending QUIT and ending the session -- with this option on,fetchmail will break a long mail retrieval session into multiplesub-sessions, sending QUIT after each sub-session. This is a gooddefense against line drops on POP3 servers. Under IMAP,fetchmail normally issues an EXPUNGE command after each deletionin order to force the deletion to be done immediately. This is safestwhen your connection to the server is flaky and expensive, as it avoidsre-sending duplicate mail after a line hit. However, on largemailboxes the overhead of re-indexing after every message can slam theserver pretty hard, so if your connection is reliable it is good to doexpunges less frequently. Also note that some servers enforce a delayof a few seconds after each quit, so fetchmail may not be able to getback in immediately after an expunge -- you may see "lock busy" errorsif this happens. If you specify this option to an integer N,it tells fetchmail to only issue expunges on every Nth delete. Anargument of zero suppresses expunges entirely (so no expunges at allwill be done until the end of run). This option does not work with ETRNor ODMR.

 

Authentication Options

-u <name> | --user <name> | --username <name>

(Keyword: user[name])
Specifies the user identification to be used when logging in to the mail server.The appropriate user identification is both server and user-dependent.The default is your login name on the client machine that is runningfetchmail.See USER AUTHENTICATION below for a complete description.

--passwordfile <filename>

(Keyword: passwordfile)
Specifies a file name from which to read the first line to use as the password.Useful if something changes the password/token often without regenerating along fetchmailrc file, such as with typical oauth2 authentication tokens.Protect the file with appropriate permissions to avoid leaking your password.Fetchmail will re-read the file for each poll when in daemon mode.

--passwordfd <integer>

(Keyword: passwordfd)
Specifies a file descriptor number inherited from the calling process,from which fetchmail should read one line to use as the password.The descriptor will usually be the receiving end of a pipe (equivalentto "something | fetchmail --passwordfd 5 5<0"),although it could also be a redirected input file(equivalent to "fetchmail --passwordfd 5 5</path/to/file").Useful if something wants to manage password ownership more securelythan files, or if the password/token changes often,such as with typical oauth2 authentication tokens. Normal interactivemode passwords requires that standard input is a terminal and disablesecho, but passwordfd does not care. Do not do somethinglike "echo 'password' | fetchmail ...", since echo's arguments arelikely to (briefly) be publicly visible in process listings.This probably doesn't interact well with deamon mode: when will itre-read a new password?

-I <specification> | --interface <specification>

(Keyword: interface)
Require that a specific interface device be up and have a specific localor remote IPv4 (IPv6 is not supported by this option yet) address (orrange) before polling. Frequently fetchmailis used over a transient point-to-point TCP/IP link established directlyto a mail server via SLIP or PPP. That is a relatively secure channel.But when other TCP/IP routes to the mail server exist (e.g., when the linkis connected to an alternate ISP), your username and password may bevulnerable to snooping (especially when daemon mode automatically pollsfor mail, shipping a clear password over the net at predictableintervals). The --interface option may be used to prevent this. Whenthe specified link is not up or is not connected to a matching IPaddress, polling will be skipped. The format is:

        interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]

The field before the first slash is the interface name (i.e., sl0, ppp0etc.). The field before the second slash is the acceptable IP address.The field after the second slash is a mask which specifies a range ofIP addresses to accept. If no mask is present 255.255.255.255 isassumed (i.e., an exact match). This option is currently only supportedunder Linux and FreeBSD. Please see the monitor section for belowfor FreeBSD specific information.

Note that this option may be removed from a future fetchmail version.

-M <interface> | --monitor <interface>

(Keyword: monitor)
Daemon mode can cause transient links which are automatically taken downafter a period of inactivity (e.g., PPP links) to remain upindefinitely. This option identifies a system TCP/IP interface to bemonitored for activity. After each poll interval, if the link is up butno other activity has occurred on the link, then the poll will beskipped. However, when fetchmail is woken up by a signal, themonitor check is skipped and the poll goes through unconditionally.This option is currently only supported under Linux and FreeBSD.For the monitor and interface options to work for non rootusers under FreeBSD, the fetchmail binary must be installed setgid kmem.This would be a security hole, but fetchmail runs with the effective GIDset to that of the kmem group only when interface data is beingcollected.

Note that this option may be removed from a future fetchmail version.

--auth <type>

(Keyword: auth[enticate])
This option permits you to specify an authentication type (see USERAUTHENTICATION below for details). The possible values are any,password, kerberos_v5, gssapi,cram-md5, otp, ntlm, msn (only for POP3),external (only IMAP), implicit (ssh is understoodas alias for implicit) and oauthbearer (requires token).When any (the default) is specified, fetchmail triesfirst methods that do not require a password (EXTERNAL, GSSAPI,KERBEROS 5); and only if the server does notsupport any of those will it ship your password unencrypted. Other valuesmay be used to force various authentication methods:implicit suppresses authentication and is thus useful for IMAP PREAUTH.external suppresses authentication and is thus useful for IMAP EXTERNAL.Any value other than password, cram-md5, ntlm,msn or otp suppresses fetchmail's normal inquiry for apassword. Specify implicit when you are using an end-to-end secureconnection such as an ssh tunnel (in this case you may also want to specify--sslmode none, which see); specify external when you useTLS with client authentication and specify gssapi if you are using aprotocol variant that employs GSSAPI. Choosing KPOP protocol automaticallyselects Kerberos authentication. This option does not work with ETRN.GSSAPI service names are in line with RFC-2743 and IANA registrations, seeGeneric Security Service Application Program Interface (GSSAPI)/Kerberos/SimpleAuthentication and Security Layer (SASL) Service Names

oauthbearer expects the supplied password to be an oauth2 authenticationtoken instead of a password, as used by services like gmail.See RFC 7628 and RFC 6750. The oauthbearersetting also allows the non-standard "xoauth2" SASL scheme (usingthe same token) if the server only claims to support "xoauth2".External tools are necessary to obtainsuch tokens. Access tokens often expire fairly quickly (e.g. 1 hour),and new ones need to be generated from renewal tokens, so the"passwordfile", "passwordfd", or "pwmd_*" options may be useful. See thecontrib/fetchmail-oauth2.py script from the fetchmail source code, whichwas derived from code associated withGoogle's Oauth2 Run Through,and other oauth2 documentation. For services like gmail, an "App Password"is probably preferable if available, because it has roughly the samesecurity risks, and is a whole lot simpler to get working. "App Password"and oauthbearer both need to protect secrets on the client machine (files) andover the network (SSL/TLS). But "App Password" issometimes completely disabled by business "G-suite" administrators.

 

Miscellaneous Options

-f <pathname> | --fetchmailrc <pathname>

Specify a non-default name for the ~/.fetchmailrcrun control file. The pathname argument must be either "-" (a singledash, meaning to read the configuration from standard input) or afilename. Unless the --version option is also on, a named fileargument must have permissions no more open than 0700 (u=rwx,g=,o=) orelse be /dev/null.

-i <pathname> | --idfile <pathname>

(Keyword: idfile)
Specify an alternate name for the .fetchids file used to save messageUIDs. NOTE: since fetchmail 6.3.0, write access to the directorycontaining the idfile is required, as fetchmail writes a temporary fileand renames it into the place of the real idfile only if the temporaryfile has been written successfully. This avoids the truncation ofidfiles when running out of disk space.

--pidfile <pathname>

(Keyword: pidfile; since fetchmail v6.3.4)
Override the default location of the PID file that is used as a lock file.Default: see "ENVIRONMENT" below. Note that many places in the code anddocumentation, the term "lock file" is used. This file contains the process IDof the running fetchmail on the first line and potentially the daemon intervalon a second line.

-n | --norewrite

(Keyword: no rewrite)
Normally, fetchmail edits RFC-822 address headers (To, From, Cc,Bcc, and Reply-To) in fetched mail so that any mail IDs local to theserver are expanded to full addresses (@ and the mail server host name areappended). This enables replies on the client to get addressedcorrectly (otherwise your mailer might think they should be addressed tolocal users on the client machine!). This option disables the rewrite.(This option is provided to pacify people who are paranoid about havingan MTA edit mail headers and want to know they can prevent it, but it isgenerally not a good idea to actually turn off rewrite.)When using ETRN or ODMR, the rewrite option is ineffective.

-E <line> | --envelope <line>

(Keyword: envelope; Multidrop only)
In the configuration file, an enhanced syntax is used:
envelope [<count>] <line>

This option changes the header fetchmail assumes will carry a copyof the mail's envelope address. Normally this is 'X-Envelope-To'.Other typically found headers to carry envelope information are'X-Original-To' and 'Delivered-To'. Now, since these headers arenot standardized, practice varies. See the discussion of multidropaddress handling below. As a special case, 'envelope "Received"'enables parsing of sendmail-style Received lines. This is the default,but discouraged because it is not fully reliable.

Note that fetchmail expects the Received-line to be in a specificformat: It must contain "by host for address", wherehost must match one of the mail server names that fetchmailrecognizes for the account in question.

The optional count argument (only available in the configuration file)determines how many header lines of this kind are skipped. A count of 1means: skip the first, take the second. A count of 2 means: skip thefirst and second, take the third, and so on.

-Q <prefix> | --qvirtual <prefix>

(Keyword: qvirtual; Multidrop only)
The string prefix assigned to this option will be removed from the username found in the header specified with the envelope option(before doing multidrop name mapping or localdomain checking,if either is applicable). This option is useful if you are usingfetchmail to collect the mail for an entire domain and your ISP(or your mail redirection provider) is using qmail.One of the basic features of qmail is the Delivered-To:message header. Whenever qmail delivers a message to a local mailboxit puts the username and host name of the envelope recipient on thisline. The major reason for this is to prevent mail loops. To set upqmail to batch mail for a disconnected site the ISP-mailhost will havenormally put that site in its 'Virtualhosts' control file so it willadd a prefix to all mail addresses for this site. This results in mailsent to 'usernameAATTuserhost.userdom.dom.com' having aDelivered-To: line of the form:

Delivered-To: mbox-userstr-usernameAATTuserhost.example.com

The ISP can make the 'mbox-userstr-' prefix anything they choosebut a string matching the user host name is likely.By using the option 'envelope Delivered-To:' you can make fetchmail reliablyidentify the original envelope recipient, but you have to strip the'mbox-userstr-' prefix to deliver to the correct user.This is what this option is for.

--configdump

Parse the ~/.fetchmailrc file, interpret any command-line optionsspecified, and dump a configuration report to standard output. Theconfiguration report is a data structure assignment in the languagePython. This option is meant to be used with an interactive~/.fetchmailrc editor like fetchmailconf, written in Python.

-y | --yydebug

Enables parser debugging, this option is meant to be used by developersonly.

 

Removed Options

-T | --netsec

Removed before version 6.3.0, the required underlying inet6_apps libraryhad been discontinued and is no longer available.

 

USER AUTHENTICATION AND ENCRYPTION

All modes except ETRN require authentication of the client to the server.Normal user authentication in fetchmail is very much like theauthentication mechanism offtp(1).The correct user-id and password depend upon the underlying securitysystem at the mail server.

If the mail server is a Unix machine on which you have an ordinary useraccount, your regular login name and password are used withfetchmail.If you use the same login name on both the server and the client machines,you needn't worry about specifying a user-id with the-uoption -- the default behavior is to use your login name on theclient machine as the user-id on the server machine. If you use adifferent login name on the server machine, specify that login namewith the-uoption. E.g., if your login name is 'jsmith' on a machine named 'mailgrunt',you would start fetchmail as follows:

fetchmail -u jsmith mailgrunt

The default behavior of fetchmail is to prompt you for yourmail server password before the connection is established. This is thesafest way to use fetchmail and ensures that your password willnot be compromised. You may also specify your password in your~/.fetchmailrc file. This is convenient when usingfetchmail in daemon mode or with scripts.

 

Using passwordeval

If you do not wish to expose your cleartext passwordin your ~/.fetchmailrc file,you can use the 'passwordeval' keyword.This allows you to specify an external commandwhich produces the cleartext password as its standard output.With this, fetchmail can retrieve cleartext passwordsfrom secure mechanisms unknown to fetchmailsuch as GPG encrypted files, password managers and so on.Here is an example:

poll mailhost.netprotocol imapusername "jsmith"passwordeval "gpg --no-tty -q -d ~/.secret"

If you add a prefix of 'PRECONNECT:' (all caps)to the passwordeval command string,fetchmail will re-execute the commandbefore each connection attempt(just after any preconnect command)to obtain a fresh authentication password/token.This is useful in the case of passwords/tokenswhich have finite lifetimes (eg. OAuth2 access tokens)and will allow fetchmail to successfully work in daemon mode in such cases.

To make use of this for OAuth2 authentication(as is currently required by Google GMail and Microsoft Outlook),one needs a script which will outputa (refreshed as needed) OAuth2 access token upon invocation.(The mutt mailreader mutt_oauth2.py contributed scriptbehaves in this mannerand the fetchmail fetchmail-oauth2.py contributed scriptcould be adapted or wrapped in a shell script to work this way.See elsewhere for details on these.)With such a script,one can then configure fetchmail to retrieve, eg, Google GMail thusly:

set daemon 300poll imap.gmail.comproto imapauth oauthbeareruser usernameAATTgmail.compasswordeval "PRECONNECT: ~/bin/OAuth2.py ~/.gmail.oauth2"  : [further options]

 

Using netrc files

If you do not specify a password, and fetchmail cannot extract onefrom your ~/.fetchmailrc file, it will look for a ~/.netrcfile in your home directory before requesting one interactively; if anentry matching the mail server is found in that file, the password willbe used. Fetchmail first looks for a match on poll name; if it finds none,it checks for a match on via name. To show a practical example,a .netrc might look like this:

machine hermes.example.orglogin joepassword topsecret

You can repeat this block with different user information if you need toprovide more than one password.

This feature may allow you to avoid duplicating passwordinformation in more than one file.

The netrc file contains login information originally set forftp(1)but fetchmail understands typical constructs of this file to use it forpasswords. The syntax consists of tokens (usually in pairs with strings).Strings can be quoted with single or double quotes, as in "quoted string",to allow enclosing blanks, and a backslash (\) within a quoted string willescape the following character, so that a password can contain quote marksthemselves. Tokens are separated by spaces, tabs or newline characters.

These tokens are understood:

machine name

Identify a remote computer name for which the following tokens apply.It needs to match either fetchmail's poll or via name.

login name

Defines the user name that fetchmail would match when looking for entries.Fetchmail ignores zero-length names or entries without login.

password string

Defines the password that fetchmail will use when machine and login match thepoll/via name and the username.

default

This is like machine, but would match any name. Fetchmail ignores it.After this, no more machine sections are permitted.

account string

Fetchmail ignores this token/string pair.

macdef macro_name

Fetchmail ignores this macro definition, meaning this, the remainderof the lines, and all following lines until a blank line is found(i. e., two consecutive new-line characters). Then .netrc parsing resumes.

On mail servers that do not provide ordinary user accounts, your user-id andpassword are usually assigned by the server administrator when you apply fora mailbox on the server. Contact your server administrator if you do not knowthe correct user-id and password for your mailbox account.

 

Secure Socket Layers (SSL) and Transport Layer Security (TLS)

All retrieval protocols can use SSL or TLS wrapping for thetransport. Additionally, POP3 and IMAP retrieval can also negotiateSSL/TLS by means of STARTTLS (or STLS).

XXX FIXME You can access SSL encrypted servicesby specifying the --ssl option.FIXME: reference --sslproto --sslcertck --sslmodeYou can also do this using the "ssl" user option in the .fetchmailrcfile. With SSL encryption enabled, queries are initiated over aconnection after negotiating an SSL session, and the connection fails ifSSL cannot be negotiated. Some services, such as POP3 and IMAP, havedifferent well known ports defined for the SSL encrypted services. Theencrypted ports will be selected automatically when SSL is enabled andno explicit port is specified.

XXX FIXME If TLS or SSL is not configured,fetchmail will usually still try to useSTARTTLS somewhat opportunistically. In practice, is it still mandatorybecause --sslcertck is a default setting and implicitly requires STARTTLS.

STARTTLS connections use the same port as the unencrypted version of theprotocol and negotiate TLS via special command. The --sslcertckcommand line or sslcertck run control file option should be used toforce strict certificate checking - see below.

--sslcertck is recommended:When connecting to an SSL or TLS encrypted server, theserver presents a certificate to the client for validation. Thecertificate is checked to verify that the common name in the certificatematches the name of the server being contacted and that the effectiveand expiration dates in the certificate indicate that it is currentlyvalid. If any of these checks fail, a warning message is printed, butthe connection continues. The server certificate does not need to besigned by any specific Certifying Authority and may be a "self-signed"certificate. If the --sslcertck command line option or sslcertck runcontrol file option is used, fetchmail will instead abort if any ofthese checks fail, because it must assume that there is aman-in-the-middle attack in this scenario, hence fetchmail must notexpose clear-text passwords. Use of the sslcertck or --sslcertck optionis therefore advised; it has become the default in fetchmail 6.4.0.

Some SSL encrypted servers may request a client side certificate. A clientside public SSL certificate and private SSL key may be specified. Ifrequested by the server, the client certificate is sent to the server forvalidation. Some servers may require a valid client certificate and mayrefuse connections if a certificate is not provided or if the certificateis not valid. Some servers may require client side certificates be signedby a recognized Certifying Authority. The format for the key files andthe certificate files is that required by the underlying SSL libraries(OpenSSL in the general case).

A word of care about the use of SSL: While above mentionedsetup with self-signed server certificates retrieved over the wirescan protect you from a passive eavesdropper, it does not help against anactive attacker. It is clearly an improvement over sending thepasswords in clear, but you should be aware that a man-in-the-middleattack is trivially possible (in particular with tools such asdsniffUse of strict certificate checking with a certification authorityrecognized by server and client, or perhaps of an SSH tunnel (see belowfor some examples) is preferable if you care seriously about thesecurity of your mailbox and passwords.

 

RETR or TOP

fetchmail makes some efforts to make the server believe messageshad not been retrieved, by using the TOP command with a large number oflines when possible. TOP is a command that retrieves the full headerand a fetchmail-specified amount of body lines. It is optional andtherefore not implemented by all servers, and some are known toimplement it improperly. On many servers however, the RETR command whichretrieves the full message with header and body, sets the "seen" flag(for instance, in a web interface), whereas the TOP command does not dothat.

fetchmail will always use the RETR command if "fetchall" is set.As a workaround, fetchmail will use the RETR command onMaillennium POP3/PROXY servers (used by Comcast) to avoid a deliberateTOP misinterpretation in this server that causes message corruption.

Note that this description is true for the current version offetchmail, but the behavior may change in future versions. Inparticular, fetchmail may prefer the RETR command because the TOPcommand causes much grief on some servers and is only optional. 

ALTERNATE AUTHENTICATION FORMS/METHODS

If your fetchmail was built with Kerberos support and you specifyKerberos authentication (either with --auth or the .fetchmailrcoption authenticate kerberos_v5) it will try to get a Kerberosticket from the mailserver at the start of each query. Note: ifeither the pollname or via name is 'hesiod', fetchmail will try to useHesiod to look up the mail server.

If you use POP3 or IMAP with GSSAPI authentication, fetchmail willexpect the server to have RFC1731- or RFC1734-conforming GSSAPIcapability, and will use it. Currently this has only been tested overKerberos 5, so you are expected to already have a ticket-grantingticket. You may pass a username different from your principal nameusing the standard --user command or by the .fetchmailrcoption user.

If your IMAP daemon returns the PREAUTH response in its greeting line,fetchmail will notice this and skip the normal authentication step.This can be useful, e.g., if you start imapd explicitly using ssh.In this case you can declare the authentication value 'implicit' on thatsite entry to stop .fetchmail from asking you for a passwordwhen it starts up.

If you use client authentication with TLS1 and your IMAP daemonreturns the AUTH=EXTERNAL response, fetchmail will notice thisand will use the authentication shortcut and will not send thepassphrase. In this case you can declare the authentication value 'external'
 on that site to stop fetchmail from asking you for a passwordwhen it starts up.

If you are using POP3, and the server issues a one-time-passwordchallenge conforming to RFC1938, fetchmail will use yourpassword as a pass phrase to generate the required response. Thisavoids sending secrets over the net unencrypted.

 

ESMTP AUTH

fetchmail also supports authentication to the ESMTP server on theclient side according to RFC 4952. Supported authentication mechanismsare CRAM-MD5, PLAIN and in fetchmail 6.5.X the obsolete LOGIN.You can specify a name/password pair to be used with the keywords 'esmtpname'and 'esmtppassword'; the former defaults to the username of the calling user.

 

DAEMON MODE

 

Introducing the daemon mode

In daemon mode, fetchmail puts itself into the background and runsforever, querying each specified host and then sleeping for a givenpolling interval. 

Starting the daemon mode

There are several ways to make fetchmail work in daemon mode. On thecommand line, --daemon <interval> or -d <interval>option runs fetchmail in daemon mode. You must specify a numericargument which is a polling interval (time to wait after completing awhole poll cycle with the last server and before starting the next pollcycle with the first server) in seconds.

Example: simply invoking

fetchmail -d 900

will, therefore, poll all the hosts described in your ~/.fetchmailrcfile (except those explicitly excluded with the 'skip' verb) a bit lessoften than once every 15 minutes (exactly: 15 minutes + time that thepoll takes).

It is also possible to set a polling intervalin your ~/.fetchmailrc file by saying 'set daemon <interval>',where <interval> is an integer number of seconds. If you do this,fetchmail will always start in daemon mode unless you override it withthe command-line option --daemon 0 or -d0.

Only one daemon process is permitted per user; in daemon mode,fetchmail sets up a per-user lock file to guarantee this.(You can however cheat and set the FETCHMAILHOME environment variable toovercome this setting, but in that case, it is your responsibility tomake sure you are not polling the same server with two processes at thesame time.) 

Awakening the background daemon

Normally, calling fetchmail with a daemon in the background sends awake-up signal to the daemon and quits without output. The backgrounddaemon then starts its next poll cycle immediately. The wake-up signal,SIGUSR1, can also be sent manually. The wake-up action also clears any'wedged' flags indicating that connections have wedged due to failedauthentication or multiple timeouts. 

Terminating the background daemon

The option-qor--quitwill kill a running daemon process instead of waking it up (if thereis no such process, fetchmail will notify you).If the --quit option appears last on the command line, fetchmailwill kill the running daemon process and then quit. Otherwise,fetchmail will first kill a running daemon process and thencontinue running with the other options. 

Useful options for daemon mode

The-L <filename>or--logfile <filename>option (keyword: set logfile) is only effective when fetchmail isdetached and in daemon mode. Note that the logfile must existbefore fetchmail is run, you can use thetouch(1)command with the filename as its sole argument to create it.
This option allows you to redirect status messagesinto a specified logfile (follow the option with the logfile name). Thelogfile is opened for append, so previous messages are not deleted. Thisis primarily useful for debugging configurations. Note that fetchmaildoes not detect if the logfile is rotated, the logfile is only openedonce when fetchmail starts. You need to restart fetchmail after rotatingthe logfile and before compressing it (if applicable).
Since v6.5.0, the log file is prefixed with time stamps, in local timeand in the format "Jun 20 23:45:01 fetchmail: ". It will be localized throughthe environment variables LC_TIME (or LC_ALL) and TZ.

The--syslogoption (keyword: set syslog) allows you to redirect status and errormessages emitted to thesyslog(3)system daemon if available.Messages are logged with an id of fetchmail, the facility LOG_MAIL,and priorities LOG_ERR, LOG_ALERT or LOG_INFO.This option is intended for logging status and error messages whichindicate the status of the daemon and the results while fetching mailfrom the server(s).Error messages for command line options and parsing the .fetchmailrcfile are still written to stderr, or to the specified log file.The--nosyslogoption turns off use ofsyslog(3),assuming it is turned on in the ~/.fetchmailrc file.This option is overridden, in certain situations, by --logfile (whichsee).

The-Nor--nodetachoption suppresses backgrounding and detachment of the daemon processfrom its control terminal. This is useful for debugging or whenfetchmail runs as the child of a supervisor process such asinit(8)or Gerrit Pape'srunit(8).Note that this also causes the logfile option to be ignored.

Note that while running in daemon mode polling a IMAP2bis server,transient errors (such as DNS failures or sendmail delivery refusals)may force the fetchall option on for the duration of the next pollingcycle. This is a robustness feature. It means that if a message isfetched (and thus marked seen by the mail server) but not deliveredlocally due to some transient error, it will be re-fetched during thenext poll cycle. (The IMAP logic does not delete messages untilthey are delivered, so this problem does not arise.)

If you touch or change the ~/.fetchmailrc file while fetchmail isrunning in daemon mode, this will be detected at the beginning of thenext poll cycle. When a changed ~/.fetchmailrc is detected,fetchmail rereads it and restarts from scratch (using exec(2); no stateinformation is retained in the new instance). Note that if fetchmailneeds to query for passwords, of that if you break the~/.fetchmailrc file's syntax, the new instance will softly andsilently vanish away on startup.

 

ADMINISTRATIVE OPTIONS

The--postmaster <name>option (keyword: set postmaster) specifies the last-resort username towhich multidrop mail is to be forwarded if no matching local recipientcan be found. It is also used as destination of undeliverable mail ifthe 'bouncemail' global option is off and additionally for spam-blockedmail if the 'bouncemail' global option is off and the 'spambounce'global option is on. This option defaults to the user who invokedfetchmail.If the invoking user is root, then the default of this option isthe user 'postmaster'. Setting postmaster to the empty string causessuch mail as described above to be discarded - this however is usually abad idea.See also the description of the 'FETCHMAILUSER' environment variable inthe ENVIRONMENT section below.

The--nobouncebehaves like the "set no bouncemail" global option, which see.

The--invisibleoption (keyword: set invisible) tries to make fetchmail invisible.Normally, fetchmail behaves like any other MTA would -- it generates aReceived header into each message describing its place in the chain oftransmission, and tells the MTA it forwards to that the mail came fromthe machine fetchmail itself is running on. If the invisible optionis on, the Received header is suppressed and fetchmail tries to spoofthe MTA it forwards to into thinking it came directly from themail server host.

The--showdotsoption (keyword: set showdots) forces fetchmail to show progress dotseven if the output goes to a file or fetchmail is not in verbose mode.Fetchmail shows the dots by default when run in --verbose modeand output goes to console. This option is ignored in --silent mode.

By specifying the--tracepollsoption, you can ask fetchmail to add information to the Receivedheader on the form "polling {label} account {user}", where {label} isthe account label (from the specified rcfile, normally ~/.fetchmailrc)and {user} is the username which is used to log on to the mailserver. This header can be used to make filtering email where nouseful header information is available and you want mail fromdifferent accounts sorted into different mailboxes (this could, forexample, occur if you have an account on the same server running amailing list, and are subscribed to the list using that account). Thedefault is not adding any such header. In.fetchmailrc,this is called 'tracepolls'.

 

RETRIEVAL FAILURE MODES

The protocols fetchmail uses to talk to mail servers are next tobulletproof. In normal operation forwarding to port 25, no message isever deleted (or even marked for deletion) on the host until the SMTPlistener on the client side has acknowledged to fetchmail thatthe message has been either accepted for delivery or rejected due to aspam block.

When forwarding to an MDA, however, there is more possibilityof error. Some MDAs are 'safe' and reliably return a nonzero statuson any delivery error, even one due to temporary resource limits.Themaildrop(1)program is like this; so are most programs designed as mail transportagents, such assendmail(1),including the sendmail wrapper of Postfix andexim(1).These programs give back a reliable positive acknowledgement andcan be used with the mda option with no risk of mail loss. UnsafeMDAs, though, may return 0 even on delivery failure. If thishappens, you will lose mail.

The normal mode of fetchmail is to try to download only 'new'messages, leaving untouched (and undeleted) messages you have alreadyread directly on the server (or fetched with a previous fetchmail--keep). But you may find that messages you have already read on theserver are being fetched (and deleted) even when you do not specify--all. There are several reasons this can happen.

A potential POP3 problem might be servers that insert messagesin the middle of mailboxes (some VMS implementations of mail arerumored to do this). The fetchmail code assumes that newmessages are appended to the end of the mailbox; when this is not trueit may treat some old messages as new and vice versa. Using UIDL whilstsetting fastuidl 0 might fix this, otherwise, consider switching to IMAP.

Yet another POP3 problem is that if they cannot make temporary files in theuser's home directory, some POP3 servers will hand back anundocumented response that causes fetchmail to spuriously report "Nomail".

The IMAP code uses the presence or absence of the server flag \Seento decide whether or not a message is new. This is not the right thingto do, fetchmail should check the UIDVALIDITY and use UID, but itdoes not do that yet. Under Unix, it counts on your IMAP server to noticethe BSD-style Status flags set by mail user agents and set the \Seenflag from them when appropriate. All Unix IMAP servers we know of dothis, though it is not specified by the IMAP RFCs. If you ever trip overa server that does not, the symptom will be that messages you havealready read on your host will look new to the server. In this(unlikely) case, only messages you fetched with fetchmail --keepwill be both undeleted and marked old.

In ETRN and ODMR modes, fetchmail does not actually retrieve messages;instead, it asks the server's SMTP listener to start a queue flushto the client via SMTP. Therefore it sends only undelivered messages.

 

SPAM FILTERING

Many SMTP listeners allow administrators to set up 'spam filters' thatblock unsolicited email from specified domains. A MAIL FROM or DATA line thattriggers this feature will elicit an SMTP response which(unfortunately) varies according to the listener.

Newer versions ofsendmailreturn an error code of 571.

According to RFC2821, the correct thing to return in this situation is550 "Requested action not taken: mailbox unavailable" (the draft adds"[E.g., mailbox not found, no access, or command rejected for policyreasons].").

Older versions of theeximMTA return 501 "Syntax error in parameters or arguments".

ThepostfixMTA runs 554 as an antispam response.

Zmailermay reject code with a 500 response (followed by an enhanced statuscode that contains more information).

Return codes whichfetchmailtreats as antispam responses and discardsthe message can be set with the 'antispam' option. This is one of theonlythree circumstance under which fetchmail ever discards mail (the othersare the 552 and 553 errors described below, and the suppression ofmulti-dropped messages with a message-ID already seen).

Iffetchmailis fetching from an IMAP server, the antispam response will be detected andthe message rejected immediately after the headers have been fetched,without reading the message body. Thus, you will not pay for downloadingspam message bodies.

By default, the list of antispam responses is empty.

If the spambounce global option is on, mail that is spam-blockedtriggers an RFC1892/RFC1894 bounce message informing the originator thatwe do not accept mail from it. See also BUGS.

 

SMTP/ESMTP ERROR HANDLING

Besides the spam-blocking described above, fetchmail takes specialactions --- that may be modified by the --softbounce option --- onthe following SMTP/ESMTP error response codes

452 (insufficient system storage)

Leave the message in the server mailbox for later retrieval.

552 (message exceeds fixed maximum message size)

Delete the message from the server. Send bounce-mail to theoriginator.

553 (invalid sending domain)

Delete the message from the server. Do not even try to sendbounce-mail to the originator.

Other errors greater or equal to 500 trigger bounce mail back to theoriginator, unless suppressed by --softbounce. See also BUGS.

 

THE RUN CONTROL FILE

The preferred way to set up fetchmail is to write a.fetchmailrc file in your home directory (you may do thisdirectly, with a text editor, or indirectly via fetchmailconf).When there is a conflict between the command-line arguments and thearguments in this file, the command-line arguments take precedence.

To protect the security of your passwords,your ~/.fetchmailrc may not normally have more than 0700 (u=rwx,g=,o=)permissions;fetchmailwill complain and exit otherwise (this check is suppressed when--version is on).

You may read the .fetchmailrc file as a list of commands tobe executed whenfetchmailis called with no arguments. 

Run Control Syntax

Comments begin with a '#' and extend through the end of the line.Otherwise the file consists of a series of server entries or globaloption statements in a free-format, token-oriented syntax.

There are four kinds of tokens: grammar keywords, numbers(i.e., decimal digit sequences), unquoted strings, and quoted strings.A quoted string is bounded by double quotes and may containwhitespace (and quoted digits are treated as a string). Note thatquoted strings will also contain line feed characters if they run acrosstwo or more lines, unless you use a backslash to join lines (see below).An unquoted string is any whitespace-delimited token that is neithernumeric, string quoted nor contains the special characters ',', ';',':', or '='.

Any amount of whitespace separates tokens in server entries, but isotherwise ignored. You may use backslash escape sequences (\n for LF,\t for HT, \b for BS, \r for CR, \nnn for decimal (wherennn cannot start with a 0), \0ooo for octal, and \xhh forhex) to embed non-printable characters or string delimiters in strings.In quoted strings, a backslash at the very end of a line will cause thebackslash itself and the line feed (LF or NL, new line) character to beignored, so that you can wrap long strings. Without the backslash at theline end, the line feed character would become part of the string.

Warning:while these resemble C-style escape sequences, they are not the same.fetchmail only supports these eight styles. C supports more escapesequences that consist of backslash (\) and a single character, butdoes not support decimal codes and does not require the leading 0 inoctal notation. Example: fetchmail interprets \233 the same as \xE9(Latin small letter e with acute), where C would interpret \233 asoctal 0233 = \x9B (CSI, control sequence introducer).

Each server entry consists of one of the keywords 'poll' or 'skip',followed by a server name, followed by server options, followed by anynumber of user (or username) descriptions, followed by user options.Note: the most common cause of syntax errors is mixing up user andserver options or putting user options before the user descriptions.

For backward compatibility, the word 'server' is a synonym for 'poll'.

You can use the noise keywords 'and', 'with','has', 'wants', and 'options' anywhere in an entry to makeit resemble English. They are ignored, but can make entries mucheasier to read at a glance. The punctuation characters ':', ';' and',' are also ignored. 

Poll versus Skip

The 'poll' verb tells fetchmail to query this host when it is run withno arguments. The 'skip' verb tellsfetchmailnot to poll this host unless it is explicitly named on the commandline. (The 'skip' verb allows you to experiment with test entriessafely, or easily disable entries for hosts that are temporarily down.)

 

KEYWORD/OPTION SUMMARY

Here are the legal options. Keyword suffixes enclosed insquare brackets are optional. Those corresponding to short command-lineoptions are followed by '-' and the appropriate option letter. Ifoption is only relevant to a single mode of operation, it is noted as's' or 'm' for singledrop- or multidrop-mode, respectively.

Here are the legal global options:

Keyword	Opt	Mode	Function
set daemon	-d		Set a background poll interval in seconds.
set postmaster			Give the name of the last-resort mail recipient (default: user runningfetchmail, "postmaster" if run by the root user)
set bouncemail			Direct error mail to the sender (default)
set no bouncemail			Direct error mail to the local postmaster (as per the 'postmaster'global option above).
set no spambounce			Do not bounce spam-blocked mail (default).
set spambounce			Bounce blocked spam-blocked mail (as per the 'antispam' user option)back to the destination as indicated by the 'bouncemail' global option.Warning: Do not use this to bounce spam back to the sender - most spamis sent with false sender address and thus this option hurts innocentbystanders.
set no softbounce			Delete permanently undeliverable mail. It is recommended to use thisoption if the configuration has been thoroughly tested.
set softbounce			Keep permanently undeliverable mail as though a temporary error hadoccurred (default).
set logfile	-L		Name of a file to append error and status messages to. Only effectivein daemon mode and if fetchmail detaches. If effective, overrides setsyslog.
set pidfile	-p		Name of the PID file.
set idfile	-i		Name of the file to store UID lists in.
set syslog			Do error logging through syslog(3). May be overridden by setlogfile.
set no syslog			Turn off error logging through syslog(3). (default)
set properties			String value that is ignored by fetchmail (may be used by extensionscripts).

Here are the legal server options:

Keyword	Opt	Mode	Function
via			Specify DNS name of mail server, overriding poll name
proto[col]	-p		Specify protocol (case insensitive):POP3, IMAP, KPOP
local[domains]		m	Specify domain(s) to be regarded as local
port			Specify TCP/IP service port (obsolete, use 'service' instead).
service	-P		Specify service name (a numeric value is also allowed andconsidered a TCP/IP port number).
auth[enticate]			Set authentication type (default 'any')
timeout	-t		Server inactivity timeout in seconds (default 300)
envelope	-E	m	Specify envelope-address header name
no envelope		m	Disable looking for envelope address
qvirtual	-Q	m	Qmail virtual domain prefix to remove from user name
aka		m	Specify alternate DNS names of mail server
interface	-I		specify IP interface(s) that must be up for server poll to take place
monitor	-M		Specify IP address to monitor for activity
plugin			Specify command through which to make server connections.
plugout			Specify command through which to make listener connections.
dns		m	Enable DNS lookup for multidrop (default)
no dns		m	Disable DNS lookup for multidrop
checkalias		m	Do comparison by IP address for multidrop
no checkalias		m	Do comparison by name for multidrop (default)
interval			Only check this site every N poll cycles; N is a numeric argument.
tracepolls			Add poll tracing information to the Received header
principal			Set Kerberos principal (only useful with IMAP and kerberos)
esmtpname			Set name for RFC2554 authentication to the ESMTP server.
esmtppassword			Set password for RFC2554 authentication to the ESMTP server.
bad-header			How to treat messages with a bad header. Can be reject (default) or accept.
retrieve-error			How to behave when messages that cannot be retrieved due to a server errorare encountered. Can be abort (default), continue or markseen.idletimeout                  T{ Idle waiting timeout (in seconds), see --idle.

Here are the legal user descriptions and options:

Keyword	Opt	Mode	Function
user[name]	-u		This is the user description and must come first after serverdescription and after possible server options, and before user options. It sets the remote user name if by itself or followed by 'there', or thelocal user name if followed by 'here'.
is			Connect local and remote user names
to			Connect local and remote user names
pass[word]			Specify remote account password in cleartext
pass[word]eval			Command line run through the shell, that outputs cleartext password on stdin
passwordfile	--...		File name with password in first line.
passwordfd	--...		Inherited file descriptor from which to read one line for the password.
ssl			Connect to server over the specified base protocol using SSL encryption
sslcert			Specify file for client side public SSL certificate
sslcertck			Enable strict certificate checking and abort connection on failure.Default only since fetchmail v6.4.0.
no sslcertck			Disable strict certificate checking and permit connections to continueon failed verification. Discouraged. Should only be used together withsslfingerprint.
sslcertfile			Specify file with trusted CA certificates
sslcertpath			Specify c_rehash-ed directory with trusted CA certificates.
sslcommonname			specify the expected server certificate common name to match against.
sslfingerprint			Specify the expected server certificate finger print from an MD5 hash.Fetchmail will disconnect and log an error if it does not match.
sslkey			Specify file for client side private SSL key
sslproto			Obsolete option. See sslmode and sslprotocolversion instead.
sslprotocolversion		Specify which TLS protocol versions are allowed.
folder	-r		Specify remote folder to query
smtphost	-S		Specify smtp host(s) to forward to
fetchdomains		m	Specify domains for which mail should be fetched
smtpaddress	-D		Specify the domain to be put in RCPT TO lines
smtpname			Specify the user and domain to be put in RCPT TO lines
antispam	-Z		Specify what SMTP returns are interpreted as spam-policy blocks
mda	-m		Specify MDA for local delivery
bsmtp	-o		Specify BSMTP batch file to append to
preconnect			Command to be executed before each connection
postconnect			Command to be executed after each connection
keep	-k		Do not delete seen messages from server
flush	-F		Flush all seen messages before querying (DANGEROUS)
limitflush			Flush all oversized messages before querying
fetchall	-a		Fetch all messages whether seen or not
rewrite			Rewrite destination addresses for reply (default)
stripcr			Strip carriage returns from ends of lines
forcecr			Force carriage returns at ends of lines
pass8bits			Force BODY=8BITMIME to ESMTP listener
dropstatus			Strip Status and X-Mozilla-Status lines out of incoming mail
dropdelivered			Strip Delivered-To lines out of incoming mail
mimedecode			Convert quoted-printable to 8-bit in MIME messages
idle			Idle waiting for new messages after each poll (IMAP only)
forceidle			Idle waiting for new messages after each poll (IMAP only, forced)
no keep	-K		Delete seen messages from server (default)
no flush			Do not flush all seen messages before querying (default)
no fetchall			Retrieve only new messages (default)
no rewrite			Do not rewrite headers
no stripcr			Do not strip carriage returns (default)
no forcecr			Do not force carriage returns at EOL (default)
no pass8bits			Do not force BODY=8BITMIME to ESMTP listener (default)
no dropstatus			Do not drop Status headers (default)
no dropdelivered			Do not drop Delivered-To headers (default)
no mimedecode			Do not convert quoted-printable to 8-bit in MIME messages (default)
no idle			Do not idle waiting for new messages after each poll (IMAP only)
limit	-l		Set message size limit
warnings	-w		Set message size warning interval
batchlimit	-b		Max # messages to forward in single connect
fetchlimit	-B		Max # messages to fetch in single connect
fetchsizelimit			Max # message sizes to fetch in single transaction
fastuidl			Use binary search for first unseen message (POP3 only)
expunge	-e		Perform an expunge on every #th message (IMAP and POP3 only)
properties			String value is ignored by fetchmail (may be used by extension scripts)

All user options must begin with a user description (user or usernameoption) and follow all server descriptions and options.

In the .fetchmailrc file, the 'envelope' string argument may bepreceded by a whitespace-separated number. This number, if specified,is the number of such headers to skip over (that is, an argument of 1selects the second header of the given type). This is sometimes usefulfor ignoring bogus envelope headers created by an ISP's local deliveryagent or internal forwards (through mail inspection systems, forinstance). 

Keywords Not Corresponding To Option Switches

The 'folder' and 'smtphost' options (unlike their command-lineequivalents) can take a space- or comma-separated list of namesfollowing them.

All options correspond to the obvious command-line arguments, exceptthe following: 'via', 'interval', 'aka', 'is', 'to', 'dns'/'no dns','checkalias'/'no checkalias', 'password', 'preconnect', 'postconnect','localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no forcecr','pass8bits'/'no pass8bits' 'dropstatus/no dropstatus','dropdelivered/no dropdelivered', 'mimedecode/no mimedecode', 'no idle',and 'no envelope'.

The 'via' option is for if you want to have morethan one configuration pointing at the same site. If it is present,the string argument will be taken as the actual DNS name of themail server host to query.This will override the argument of poll, which can then simply be adistinct label for the configuration (e.g., what you would give on thecommand line to explicitly query this host).

The 'interval' option (which takes a numeric argument) allows you to poll aserver less frequently than the basic poll interval. If you say'interval N' the server this option is attached to will only bequeried every N poll intervals. 

Singledrop versus Multidrop options

Please ensure you read the section titledTHE USE AND ABUSE OF MULTIDROP MAILBOXES if you intend to use multidrop mode.

The 'is' or 'to' keywords associate the following local (client)name(s) (or server-name to client-name mappings separated by =) withthe mail server user name in the entry. If an is/to list has '*' asits last name, unrecognized names are simply passed through. Note thatuntil fetchmail version 6.3.4 inclusively, these lists could onlycontain local parts of user names (fetchmail would only look at the partbefore the @ sign). fetchmail versions 6.3.5 andnewer support full addresses on the left hand side of these mappings,and they take precedence over any 'localdomains', 'aka', 'via' orsimilar mappings.

A single local name can be used to support redirecting your mail whenyour username on the client machine is different from your name on themail server. When there is only a single local name, mail is forwardedto that local username regardless of the message's Received, To, Cc,and Bcc headers. In this case,fetchmailnever does DNS lookups.

When there is more than one local name (or name mapping),fetchmail looks at the envelope header, if configured, andotherwise at the Received, To, Cc, and Bcc headers of retrieved mail(this is 'multidrop mode'). It looks for addresses with host name partsthat match your poll name or your 'via', 'aka' or 'localdomains'options, and usually also for host name parts which DNS tells it arealiases of the mail server. See the discussion of 'dns', 'checkalias','localdomains', and 'aka' for details on how matching addresses arehandled.

If fetchmail cannot match any mail server usernames orlocaldomain addresses, the mail will be bounced.Normally it will be bounced to the sender, but if the 'bouncemail'global option is off, the mail will go to the local postmaster instead.(see the 'postmaster' global option). See also BUGS.

The 'dns' option (normally on) controls the way addresses frommultidrop mailboxes are checked. On, it enables logic to check eachhost address that does not match an 'aka' or 'localdomains' declarationby looking it up with DNS. When a mail server username is recognizedattached to a matching host name part, its local mapping is added tothe list of local recipients.

The 'checkalias' option (normally off) extends the lookups performedby the 'dns' keyword in multidrop mode, providing a way to cope withremote MTAs that identify themselves using their canonical name, whilethey are polled using an alias.When such a server is polled, checks to extract the envelope addressfail, and fetchmail reverts to delivery using the To/Cc/Bccheaders (See below 'Header versus Envelope addresses').Specifying this option instructs fetchmail to retrieve all the IPaddresses associated with both the poll name and the name used by theremote MTA and to do a comparison of the IP addresses. This comes inhandy in situations where the remote server undergoes frequent canonicalname changes, that would otherwise require modifications to the rcfile.'checkalias' has no effect if 'no dns' is specified in the rcfile.

The 'aka' option is for use with multidrop mailboxes. It allows youto pre-declare a list of DNS aliases for a server. This is anoptimization hack that allows you to trade space for speed. Whenfetchmail, while processing a multidrop mailbox, grovels throughmessage headers looking for names of the mail server, pre-declaringcommon ones can save it from having to do DNS lookups. Note: the namesyou give as arguments to 'aka' are matched as suffixes -- if you specify(say) 'aka netaxs.com', this will match not just a host name netaxs.com,but any host name that ends with '.netaxs.com'; such as (say)pop3.netaxs.com and mail.netaxs.com.

The 'localdomains' option allows you to declare a list of domainswhich fetchmail should consider local. When fetchmail is parsingaddress lines in multidrop modes, and a trailing segment of a hostname matches a declared local domain, that address is passed throughto the listener or MDA unaltered (local-name mappings are notapplied).

If you are using 'localdomains', you may also need to specify 'noenvelope', which disables fetchmail's normal attempt to deducean envelope address from the Received line or X-Envelope-To header orwhatever header has been previously set by 'envelope'. If you set 'noenvelope' in the defaults entry it is possible to undo that inindividual entries by using 'envelope <string>'. As a special case,'envelope "Received"' restores the default parsing ofReceived lines.

The password option requires a string argument, which is the passwordto be used with the entry's server.

The 'preconnect' keyword allows you to specify a shell command to beexecuted just before each timefetchmailestablishes a mail server connection. This may be useful if you areattempting to set up secure POP connections with the aid ofssh(1).If the command returns a nonzero status, the poll of that mail serverwill be aborted.

Similarly, the 'postconnect' keyword similarly allows you to specify ashell command to be executed just after each time a mail serverconnection is taken down.

The 'forcecr' option controls whether lines terminated by LF only aregiven CRLF termination before forwarding. Strictly speaking RFC821requires this, but few MTAs enforce the requirement so this optionis normally off (only one such MTA, qmail, is in significant use attime of writing).

The 'stripcr' option controls whether carriage returns are strippedout of retrieved mail before it is forwarded. It is normally notnecessary to set this, because it defaults to 'on' (CR strippingenabled) when there is an MDA declared but 'off' (CR strippingdisabled) when forwarding is via SMTP. If 'stripcr' and 'forcecr' areboth on, 'stripcr' will override.

The 'pass8bits' option exists to cope with Microsoft mail programs thatstupidly slap a "Content-Transfer-Encoding: 7bit" on everything. Withthis option off (the default) and such a header present,fetchmaildeclares BODY=7BIT to an ESMTP-capable listener; this causes problems formessages actually using 8-bit ISO or KOI-8 character sets, which willbe garbled by having the high bits of all characters stripped. If'pass8bits' is on,fetchmailis forced to declare BODY=8BITMIME to any ESMTP-capable listener. Ifthe listener is 8-bit-clean (as all the major ones now are) the rightthing will probably result.

The 'dropstatus' option controls whether nonempty Status andX-Mozilla-Status lines are retained in fetched mail (the default) ordiscarded. Retaining them allows your MUA to see what messages (ifany) were marked seen on the server. On the other hand, it canconfuse some new-mail notifiers, which assume that anything with aStatus line in it has been seen. (Note: the empty Status linesinserted by some buggy POP servers are unconditionally discarded.)

The 'dropdelivered' option controls whether Delivered-To headers willbe kept in fetched mail (the default) or discarded. These headers areadded by qmail and Postfix mail servers in order to avoid mail loops butmay get in your way if you try to "mirror" a mail server within the samedomain. Use with caution.

The 'mimedecode' option controls whether MIME messages using thequoted-printable encoding are automatically converted into pure 8-bitdata. If you are delivering mail to an ESMTP-capable, 8-bit-cleanlistener (that includes all of the major MTAs like sendmail), thenthis will automatically convert quoted-printable message headers anddata into 8-bit data, making it easier to understand when readingmail. If your e-mail programs know how to deal with MIME messages,then this option is not needed. The mimedecode option is off bydefault, because doing RFC2047 conversion on headers throws awaycharacter-set information and can lead to bad results if the encodingof the headers differs from the body encoding.

The 'idle' option is intended to be used with IMAP servers supportingthe RFC2177 IDLE command extension, but does not strictly require it.If it is enabled, and fetchmail detects that IDLE is supported, anIDLE will be issued at the end of each poll. This will tell the IMAPserver to hold the connection open and notify the client when new mailis available. If IDLE is not supported, fetchmail will simulate it byperiodically issuing NOOP. If you need to poll a link frequently, IDLEcan save bandwidth by eliminating TCP/IP connects and LOGIN/LOGOUTsequences. On the other hand, an IDLE connection will eat almost allof your fetchmail's time, because it will never drop the connectionand allow other polls to occur unless the server times out the IDLE.It also does not work with multiple folders; only the first folder willever be polled.

The 'properties' option is an extension mechanism. It takes a stringargument, which is ignored by fetchmail itself. The string argument may beused to store configuration information for scripts which require it.In particular, the output of '--configdump' option will make propertiesassociated with a user entry readily available to a Python script. 

Miscellaneous Run Control Options

The words 'here' and 'there' have useful English-likesignificance. Normally 'user eric is esr' would mean thatmail for the remote user 'eric' is to be delivered to 'esr',but you can make this clearer by saying 'user eric there is esr here',or reverse it by saying 'user esr here is eric there'

Legal protocol identifiers for use with the 'protocol' keyword are:

    auto (or AUTO) (legacy, to be removed from future release)    pop3 (or POP3)      kpop (or KPOP) (a Kerberos-based variant)    imap (or IMAP)

Legal authentication types are 'any', 'password','kerberos_v5' and 'gssapi', 'implicit', 'external' (only for IMAP),'oauthbearer' (requires authentication token in place of password).The 'password' type specifiesauthentication by normal transmission of a password;'kerberos_v5' tells fetchmail to try to get a Kerberos ticket at thestart of each query instead, and send an arbitrary string as thepassword; and 'gssapi' tells fetchmail to use GSSAPI authentication.See the description of the 'auth' keyword for more.

Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V5authentication. These defaults may be overridden by later options.

There are some global option statements: 'set logfile'followed by a string sets the same global specified by --logfile. Acommand-line --logfile option will override this. Note that --logfile isonly effective if fetchmail detaches itself from the terminal, is indaemon mode, and if thelogfile already exists before fetchmail is run, and it overrides--syslog in this case. Also,'set daemon' sets the poll interval as --daemon does. This can beoverridden by a command-line --daemon option; in particular --daemon~0can be used to force foreground operation. The 'set postmaster'statement sets the address to which multidrop mail defaults if there areno local matches. Finally, 'set syslog' sends log messages tosyslogd(8).

 

DEBUGGING FETCHMAIL

 

Fetchmail crashing

There are various ways in that fetchmail may "crash", i. e. stopoperation suddenly and unexpectedly. A "crash" usually refers to anerror condition that the software did not handle by itself. A well-knownfailure mode is the "segmentation fault" or "signal 11" or "SIGSEGV" orjust "segfault" for short. These can be caused by hardware or by softwareproblems. Software-induced segfaults can usually be reproduced easilyand in the same place, whereas hardware-induced segfaults can go away ifthe computer is rebooted, or powered off for a few hours, and can happenin random locations even if you use the software the same way.

For solving hardware-induced segfaults, find the faulty component and repair orreplace it.The Sig11 FAQmay help you with details.

For solving software-induced segfaults, the developers may need a "stackbacktrace".

 

Enabling fetchmail core dumps

By default, fetchmail suppresses core dumps as these might containpasswords and other sensitive information. For debugging fetchmailcrashes, obtaining a "stack backtrace" from a core dump is often thequickest way to solve the problem, and when posting your problem on amailing list, the developers may ask you for a "backtrace".

1. To get useful backtraces, fetchmail needs to be installed withoutgetting stripped of its compilation symbols. Unfortunately, mostbinary packages that are installed are stripped, and core files fromsymbol-stripped programs are worthless. So you may need to recompilefetchmail. On many systems, you can type

        file `which fetchmail`

to find out if fetchmail was symbol-stripped or not. If yours wasunstripped, fine, proceed, if it was stripped, you need to recompile thesource code first. You do not usually need to install fetchmail in orderto debug it.

2. The shell environment that starts fetchmail needs to enable coredumps. The key is the "maximum core (file) size" that can usually beconfigured with a tool named "limit" or "ulimit". See the documentationfor your shell for details. In the popular bash shell, "ulimit -Scunlimited" will allow the core dump.

3. You need to tell fetchmail, too, to allow core dumps. To dothis, run fetchmail with the -d0 -v options. It is often easierto also add --nosyslog -N as well.

Finally, you need to reproduce the crash. You can just start fetchmailfrom the directory where you compiled it by typing ./fetchmail,so the complete command line will start with ./fetchmail -Nvd0--nosyslog and perhaps list your other options.

After the crash, run your debugger to obtain the core dump. Thedebugger will often be GNU GDB, you can then type (adjust paths asnecessary) gdb ./fetchmail fetchmail.core and then, after GDBhas started up and read all its files, type backtrace full, savethe output (copy & paste will do, the backtrace will be read by a human)and then type quit to leave gdb.Note:on some systems, the corefiles have different names, they might contain a number instead of theprogram name, or number and name, but it will usually have "core" aspart of their name.

 

INTERACTION WITH RFC 822

When trying to determine the originating address of a message,fetchmail looks through headers in the following order:

        Return-Path:        Resent-Sender: (ignored if it does not contain an @ or !)        Sender: (ignored if it does not contain an @ or !)        Resent-From:        From:        Reply-To:        Apparently-From:

The originating address is used for logging, and to set the MAIL FROMaddress when forwarding to SMTP. This order is intended to copegracefully with receiving mailing list messages in multidrop mode. Theintent is that if a local address does not exist, the bounce messagewill not be returned blindly to the author or to the list itself, butrather to the list manager (which is less annoying).

In multidrop mode, destination headers are processed as follows:First, fetchmail looks for the header specified by the 'envelope' optionin order to determine the local recipient address. If the mail isaddressed to more than one recipient, the Received line will not containany information regarding recipient addresses.

Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc:lines. If they exist, they should contain the final recipients andhave precedence over their To:/Cc:/Bcc: counterparts. If the Resent-*lines do not exist, the To:, Cc:, Bcc: and Apparently-To: lines arelooked for. (The presence of a Resent-To: is taken to imply that theperson referred by the To: address has already received the originalcopy of the mail.)

 

CONFIGURATION EXAMPLES

Note that although there are password declarations in a good manyof the examples below, this is mainly for illustrative purposes.We recommend stashing account/password pairs in your $HOME/.netrcfile, where they can be used not just by fetchmail but by ftp(1) andother programs.

The basic format is:

poll SERVERNAME protocol PROTOCOL username NAMEpassword PASSWORD

Example:

poll pop.provider.net protocol pop3 username "jsmith" password "secret1"

Or, using some abbreviations:

poll pop.provider.net proto pop3 user "jsmith" password "secret1"

Multiple servers may be listed:

poll pop.provider.net proto pop3 user "jsmith" pass "secret1"poll other.provider.net proto imap user "John.Smith" pass "My^Hat"

Here is the same version with more whitespace and some noise words:

poll pop.provider.net proto pop3     user "jsmith", with password secret1, is "jsmith" here;poll other.provider.net proto imap:     user "John.Smith", with password "My^Hat", is "John.Smith" here;

If you need to include whitespace in a parameter string or start thelatter with a number, enclose the string in double quotes. Thus:

poll mail.provider.net with proto pop3:     user "jsmith" there has password "4u but u cannot krak this"     is jws here and wants mda "/bin/mail"

You may have an initial server description headed by the keyword'defaults' instead of 'poll' followed by a name. Such a recordis interpreted as defaults for all queries to use. It may be overwrittenby individual server descriptions. So, you could write:

defaults proto pop3     user "jsmith"poll pop.provider.net     pass "secret1"poll mail.provider.net     user "jjsmith" there has password "secret2"

It is possible to specify more than one user per server.The 'user' keyword leads off a user description, and every user specificationin a multi-user entry must include it. Here is an example:

poll pop.provider.net proto pop3 port 3111     user "jsmith" with pass "secret1" is "smith" here     user jones with pass "secret2" is "jjones" here keep

This associates the local username 'smith' with the pop.provider.netusername 'jsmith' and the local username 'jjones' with thepop.provider.net username 'jones'. Mail for 'jones' is kept on theserver after download.

Here is what a simple retrieval configuration for a multidrop mailboxlooks like:

poll pop.provider.net:     user maildrop with pass secret1 to golux 'hurkle'='happy' snark here

This says that the mailbox of account 'maildrop' on the server is amultidrop box, and that messages in it should be parsed for theserver user names 'golux', 'hurkle', and 'snark'. It furtherspecifies that 'golux' and 'snark' have the same name on theclient as on the server, but mail for server user 'hurkle' should bedelivered to client user 'happy'.

Note that fetchmail, until version 6.3.4, did NOT allow fulluserAATTdomain specifications here, these would never match.Fetchmail 6.3.5 and newer support userAATTdomain specifications onthe left-hand side of a user mapping.

Here is an example of another kind of multidrop connection:

poll pop.provider.net localdomains loonytoons.org toons.org     envelope X-Envelope-To     user maildrop with pass secret1 to * here

This also says that the mailbox of account 'maildrop' on the server isa multidrop box. It tells fetchmail that any address in theloonytoons.org or toons.org domains (including sub-domain addresses like'joeAATTdaffy.loonytoons.org') should be passed through to the local SMTPlistener without modification. Be careful of mail loops if you do this!

Here is an example configuration using ssh and the plugin option. Thequeries are made directly on the stdin and stdout of imapd via ssh.Note that in this setup, IMAP authentication can be skipped.

poll mailhost.net with proto imap:     plugin "ssh %h /usr/sbin/imapd" auth implicit;     user esr is esr here

 

THE USE AND ABUSE OF MULTIDROP MAILBOXES

Use the multiple-local-recipients feature with caution -- it can bite.All multidrop features are ineffective in ETRN and ODMR modes.

Also, note that in multidrop mode duplicate mails may be suppressed.A piece of mail is considered duplicate if it does not have a discernibleenvelope recipient address, has the same header asthe message immediately preceding and more than one addressee. Suchruns of messages may be generated when copies of a message addressedto multiple users are delivered to a multidrop box. (To be precise,fetchmail 6.2.5 through 6.4.X use an MD5 hash of the raw message header,and only fetchmail 6.4.16+ document this properly.Fetchmail 5.0.8 (1999-09-14) through 6.2.4 used only the Message-ID header.5.0.7 and older did not suppress duplicates.)

Note that this duplication killer code checking the entire header isvery restrictive and may not suppress many duplicates in practice - forinstance, if some X-Original-To or Delivered-To header differs. This isintentional and correct in such situations: wherever envelope information isavailable, it should be used for reliable delivery of mailing list and blindcarbon copy (Bcc) messages. See the subsection Duplicate suppression belowfor suggestions.

 

Header versus Envelope addresses

The fundamental problem is that by having your mail server toss severalpeoples' mail in a single maildrop box, you may have thrown awaypotentially vital information about who each piece of mail wasactually addressed to (the 'envelope address', as opposed to theheader addresses in the RFC822 To/Cc headers - the Bcc is not availableat the receiving end). This 'envelope address' is the address you needin order to reroute mail properly.

Sometimesfetchmailcan deduce the envelope address. If the mail server MTA issendmailand the item of mail had just one recipient, the MTA will have writtena 'by/for' clause that gives the envelope addressee into its Receivedheader. But this does not work reliably for other MTAs, nor if there ismore than one recipient. By default, fetchmail looks forenvelope addresses in these lines; you can restore this default with-E "Received" or 'envelope Received'.

As a better alternative,some SMTP listeners and/or mail servers insert a headerin each message containing a copy of the envelope addresses. Thisheader (when it exists) is often 'X-Original-To', 'Delivered-To' or'X-Envelope-To'. Fetchmail's assumption about this can be changed withthe -E or 'envelope' option. Note that writing an envelope header ofthis kind exposes the names of recipients (including blind-copyrecipients) to all receivers of the messages, so the upstream must storeone copy of the message per recipient to avoid becoming a privacy problem.

Postfix, since version 2.0, writes an X-Original-To: header whichcontains a copy of the envelope as it was received.

Qmail and Postfix generally write a 'Delivered-To' header upondelivering the message to the mail spool and use it to avoid mail loops.Qmail virtual domains however will prefix the user name with a stringthat normally matches the user's domain. To remove this prefix you canuse the -Q or 'qvirtual' option.

Sometimes, unfortunately, neither of these methods works. That is thepoint when you should contact your ISP and ask them to provide such anenvelope header, and you should not use multidrop in this situation.When they all fail, fetchmail must fall back on the contents of To/Ccheaders (Bcc headers are not available - see below) to try to determinerecipient addressees -- and these are unreliable.In particular, mailing-list software often ships mail with onlythe list broadcast address in the To: header.

Note that a future version of fetchmail may remove To/Cc parsing!

Whenfetchmailcannot deduce a recipient address that is local, and the intendedrecipient address was anyone other than fetchmail's invoking user,mail will get lost.This is what makes the multidrop feature risky without proper envelopeinformation.

A related problem is that when you blind-copy a mail message, the Bccinformation is carried only as envelope address (it is removed fromthe headers by the sending mail server, so fetchmail can see it only ifthere is an X-Envelope-To header). Thus, blind-copying to someone whogets mail over a fetchmail multidrop link will fail unless themail server host routinely writes X-Envelope-To or an equivalent headerinto messages in your maildrop.

In conclusion, mailing lists and Bcc'd mail can only work if theserver you are fetching from

(1)

stores one copy of the message per recipient in your domain and

(2)

records the envelope information in a special header (X-Original-To,Delivered-To, X-Envelope-To).

 

Good Ways To Use Multidrop Mailboxes

Multiple local names can be used to administer a mailing list from theclient side of a fetchmail collection. Suppose your name is'esr', and you want to both pick up your own mail and maintain a mailinglist called (say) "fetchmail-friends", and you want to keep the aliaslist on your client machine.

On your server, you can alias 'fetchmail-friends' to 'esr'; then, inyour .fetchmailrc, declare 'to esr fetchmail-friends here'.Then, when mail including 'fetchmail-friends' as a local addressgets fetched, the list name will be appended to the list ofrecipients your SMTP listener sees. Therefore it will undergo aliasexpansion locally. Be sure to include 'esr' in the local aliasexpansion of fetchmail-friends, or you will never see mail sent only tothe list. Also be sure that your listener has the "me-too" option set(sendmail's -oXm command-line option or OXm declaration) so your nameis not removed from alias expansions in messages you send.

This trick is not without its problems, however. You will begin to seethis when a message comes in that is addressed only to a mailing listyou do not have declared as a local name. Each such messagewill feature an 'X-Fetchmail-Warning' header which is generatedbecause fetchmail cannot find a valid local name in the recipientaddresses. Such messages default (as was described above) to beingsent to the local user running fetchmail, but the program has noway to know that this is actually the right thing.

 

Bad Ways To Abuse Multidrop Mailboxes

Multidrop mailboxes andfetchmailserving multiple users in daemon mode do not mix. The problem, again, ismail from mailing lists, which typically does not have an individualrecipient address on it. Unlessfetchmailcan deduce an envelope address, such mail will only go to the accountrunning fetchmail (probably root). Also, blind-copied users are verylikely never to see their mail at all.

If you are tempted to use fetchmailto retrieve mail for multiple users from a single mail drop via POP orIMAP, think again (and reread the section on header and envelopeaddresses above). It would be smarter to just let the mail sit in themail server's queue and use fetchmail's ETRN or ODMR modes to triggerSMTP sends periodically (of course, this means you have to poll morefrequently than the mail server's expiry period). If you cannot arrangethis, try setting up a UUCP feed.

If you absolutely must use multidrop for this purpose, make sureyour mail server writes an envelope-address header that fetchmail cansee. Otherwise you will lose mail and it will come backto haunt you.

 

Speeding Up Multidrop Checking

Normally, when multiple users are declaredfetchmailextracts recipient addresses as described above and checks each hostpart with DNS to see if it is an alias of the mail server. If so, thename mappings described in the "to ... here" declaration are done andthe mail locally delivered.

This is a convenient but also slow method. To speedit up, pre-declare mail server aliases with 'aka'; these are checkedbefore DNS lookups are done. If you are certain your aka list containsallDNS aliases of the mail server (and all MX names pointing at it - notethis may change in a future version)you can declare 'no dns' to suppress DNS lookups entirely andonly match against the aka list.

 

Duplicate suppression on multidrop

If fetchmail's duplicate suppression code does not kick in for yourmultidrop mail account, other options is using sieve, or for instanceCourier's maildrop package (and in particular, its reformail programwith the -D option) as the delivery agent (either from fetchmail,or from your local mail server that fetchmail injects into).

 

SOCKS

Support for socks4/5 is a compile time configuration option. Oncecompiled in, fetchmail will always use the socks libraries andconfiguration on your system, there are no run-time switches infetchmail - but you can still configure SOCKS: you can specify whichSOCKS configuration file is used in the SOCKS_CONF environmentvariable.

For instance, if you wanted to bypass the SOCKS proxy altogether andhave fetchmail connect directly, you could just passSOCKS_CONF=/dev/null in the environment, for example (add your usualcommand line options - if any - to the end of this line):

env SOCKS_CONF=/dev/null fetchmail

 

EXIT CODES

To facilitate the use offetchmailin shell scripts, an exit status code is returned to give an indicationof what occurred during a given connection.

The exit codes returned byfetchmailare as follows:

0

One or more messages were successfully retrieved (or, if the -c optionwas selected, were found waiting but not retrieved).

1

There was no mail awaiting retrieval. (There may have been old mail stillon the server but not selected for retrieval.) If you do not want "nomail" to be an error condition (for instance, for cron jobs), use aPOSIX-compliant shell and add

|| [ $? -eq 1 ]

to the end of the fetchmail command line, note that this leaves 0untouched, maps 1 to 0, and maps all other codes to 1. See also item #C8in the FAQ.

2

An error was encountered when attempting to open a socket to retrievemail. If you do not know what a socket is, do not worry about it --just treat this as an 'unrecoverable error'. This error can also bebecause a protocol fetchmail wants to use is not listed in /etc/services.

3

The user authentication step failed. This usually means that a baduser-id or password was specified. Or it may mean that youtried to run fetchmail under circumstances where it did not havestandard input attached to a terminal and could not prompt for amissing password.

4

Some sort of fatal protocol error was detected.

5

There was a syntax error in the arguments tofetchmail, or a pre- or post-connect command failed.

6

The run control file had bad permissions.

7

There was an error condition reported by the server. Can alsofire if fetchmail timed out while waiting for the server.

8

Client-side exclusion error. This meansfetchmaileither found another copy of itself already running, or failed in sucha way that it is not sure whether another copy is running.

9

The user authentication step failed because the server responded "lockbusy". Try again after a brief pause! This error is not implementedfor all protocols, nor for all servers. If not implemented for yourserver, "3" will be returned instead, see above. May be returned whentalking to qpopper or other servers that can respond with "lock busy"or some similar text containing the word "lock".

10

Thefetchmailrun failed while trying to do an SMTP port open or transaction.

11

Fatal DNS error. Fetchmail encountered an error while performinga DNS lookup at startup and could not proceed.

12

BSMTP batch file could not be opened.

13

Poll terminated by a fetch limit (see the --fetchlimit option).

14

Server busy indication.

23

Internal error. You should see a message on standard error withdetails.

24 - 26, 28, 29

These are internal codes and should not appear externally.

Whenfetchmailqueries more than one host, return status is 0 if any querysuccessfully retrieved mail. Otherwise the returned error status isthat of the last host queried.

 

FILES

~/.fetchmailrc, $HOME/.fetchmailrc, $HOME_ETC/.fetchmailrc, $FETCHMAILHOME/fetchmailrc

default run control file (location can be overridden with environment variables)

~/.fetchids, $HOME/.fetchids, $HOME_ETC/.fetchids, $FETCHMAILHOME/.fetchids

default location of file recording last message UIDs seen per host.(location can be overridden with environment variables)

~/.fetchmail.pid, $HOME/.fetchmail.pid, $HOME_ETC/.fetchmail.pid, $FETCHMAILHOME/fetchmail.pid

default location of lock file (sometimes called pidfile or PID file, see optionpidfile) to help prevent concurrent runs (non-root mode).(location can be overridden with environment variables)

~/.netrc, $HOME/.netrc, $HOME_ETC/.netrc

your FTP run control file, which (if present) will be searched forpasswords as a last resort before prompting for one interactively.(location can be overridden with environment variables)

/var/run/fetchmail.pid

lock file (pidfile) to help prevent concurrent runs (root mode, Linux systems).

/etc/fetchmail.pid

lock file (pidfile) to help prevent concurrent runs (root mode, systems without/var/run).

 

ENVIRONMENT

Fetchmail's behavior can be altered by providing it with environment variables.Some may alter the operation of libraries that fetchmail links against, forinstance, OpenSSL.Note that in daemon mode, you will need to quit the background daemon processand start a new fetchmail daemon for environment changes to take effect.

FETCHMAILHOME

If this environment variable is set to a valid andexisting directory name, fetchmail will read $FETCHMAILHOME/fetchmailrc(the dot is missing in this case), $FETCHMAILHOME/.fetchids (keeping its dot)and $FETCHMAILHOME/fetchmail.pid (without dot) rather than from the user'shome directory. The .netrc file is always looked for in the invokinguser's home directory (or $HOME_ETC) regardless of FETCHMAILHOME's setting.

FETCHMAILUSER

If this environment variable is set, it is used as the name of thecalling user (default local name) for purposes such as mailing errornotifications. Otherwise, if either the LOGNAME or USER variable iscorrectly set (e.g., the corresponding UID matches the session user ID)then that name is used as the default local name. Otherwisegetpwuid(3) must be able to retrieve a password entry for thesession ID (this elaborate logic is designed to handle the case ofmultiple names per user ID gracefully).

FETCHMAIL_DISABLE_CBC_IV_COUNTERMEASURE

(since v6.3.22):If this environment variable is set and not empty, fetchmail will disablea countermeasure against an SSL CBC IV attack (by settingSSL_OP_DONT_INSERT_EMPTY_FRAGMENTS). This is a security risk, but may benecessary for connecting to certain non-standards-conforming servers.See fetchmail's NEWS file and fetchmail-SA-2012-01.txt for details.Earlier fetchmail versions (v6.3.21 and older) used to disable thiscountermeasure, but v6.3.22 no longer does that as a safety precaution.

FETCHMAIL_POP3_FORCE_RETR

(since v6.3.9):If this environment variable is defined at all (even if empty), fetchmailwill forgo the POP3 TOP command and always use RETR. This can beused as a workaround when TOP does not work properly.

FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS

(since v6.3.17):If this environment variable is set and not empty, fetchmail will always loadthe default X.509 trusted certificate locations for SSL/TLS CA certificates,even if --sslcertfile and --sslcertpath are given.The latter locations take precedence over the system default locations.This is useful in case there are broken certificates in the system directoriesand the user has no administrator privileges to remedy the problem.

FETCHMAIL_WOLFSSL_DEBUG

(since v6.4.25):If fetchmail is compiled and linked with wolfSSL, if wolfSSL was built with--enable-debug, and if this environment variable is set and not empty,then enable wolfSSL's debug mode. This will emit huge amounts of debug outputto stderr.

HOME

(documented since 6.4.1):This variable is normally set to the user's home directory. If it is setto a different directory than what is in the password database, HOME takesprecedence.

HOME_ETC

(documentation corrected to match behaviour of code since 6.4.1):If the HOME_ETC variable is set, it will override fetchmail's idea of $HOME,i. e. fetchmail will read .fetchmailrc, .fetchids, .fetchmail.pid and .netrcfrom $HOME_ETC instead of $HOME (or if HOME is also unset,from the passwd file's home directory location).

If HOME_ETC and FETCHMAILHOME are both set, FETCHMAILHOME takes precedenceand HOME_ETC will be ignored.

SOCKS_CONF

(only if SOCKS support is compiled in) this variable is used by thesocks library to find out which configuration file it should read. Setthis to /dev/null to bypass the SOCKS proxy.

SSL_CERT_DIR

(with truly OpenSSL 3.0 compatible library): overrides OpenSSL's ideaof the default trust directory or path (which contains individual certificatefiles and hashed symlinks), see the SSL_CTX_set_default_verify_paths(3)manual page for details, it may be in the openssl development package.If using another library's OpenSSL compatibility interface, this may not work.Since this variable only specifies a default value, the option --sslcertpathtakes precedence if given.

SSL_CERT_FILE

(with truly OpenSSL 3.0 compatible library): overrides OpenSSL's ideaof the default trust certificate bundle file (which contains a concatenationof base64-encoded certificates in PEM format), see theSSL_CTX_set_default_verify_paths(3) manual pagefor details, it may be in the openssl development package.If using another library's OpenSSL compatibility interface, this may not work.Since this variable only specifies a default value, the option --sslcertfiletakes precedence if given.

other system default variables

such as TZ or the locale LC_XXX variables,will also influence program behaviour.

 

SIGNALS

If a fetchmail daemon is running as root, SIGUSR1 wakes it up from itssleep phase and forces a poll of all non-skipped servers. For compatibilityreasons, SIGHUP can also be used in 6.3.X but may not be available in futurefetchmail versions.

If fetchmail is running in daemon mode as non-root, use SIGUSR1 to wakeit (this is so SIGHUP due to logout can retain the default action of killingit).

Running fetchmail in foreground while a background fetchmail isrunning will do whichever of these is appropriate to wake it up.

 

BUGS, LIMITATIONS, AND KNOWN PROBLEMS

Please check the NEWS file that shipped with fetchmail for moreknown bugs than those listed here.

Fetchmail cannot handle user names that contain blanks after a "@"character, for instance "demonstr@ti on". These are rather uncommon andonly hurt when using UID-based --keep setups, so the 6.X.Y versions offetchmail will not be fixed.

Fetchmail cannot handle configurations where you have multiple accountsthat use the same server name and the same login. Any userAATTservercombination must be unique.

The assumptions that the DNS and in particular the checkalias optionsmake are not often sustainable. For instance, it has become uncommon foran MX server to be a POP3 or IMAP server at the same time. Therefore theMX lookups may go away in a future release.

The mda and plugin options interact badly. In order to collect errorstatus from the MDA, fetchmail has to change its normal signalhandling so that dead plugin processes do not get reaped until the endof the poll cycle. This can cause resource starvation if too manyzombies accumulate. So either do not deliver to a MDA using plugins orrisk being overrun by an army of undead.

The --interface option does not support IPv6 and it is doubtful if itever will, since there is no portable way to query interface IPv6addresses.

The RFC822 address parser used in multidrop mode chokes on some@-addresses that are technically legal but bizarre. Strange uses ofquoting and embedded comments are likely to confuse it.

In a message with multiple envelope headers, only the last oneprocessed will be visible to fetchmail.

Use of some of these protocols requires that the program sendunencrypted passwords over the TCP/IP connection to the mail server.This creates a risk that name/password pairs might be snaffled with apacket sniffer or more sophisticated monitoring software. Under Linuxand FreeBSD, the --interface option can be used to restrict polling toavailability of a specific interface device with a specific local orremote IP address, but snooping is still possible if (a) either hosthas a network device that can be opened in promiscuous mode, or (b)the intervening network link can be tapped. We recommend the use ofssh(1)tunnelling to not only shroud your passwords but encrypt the entireconversation.

Use of the %F or %T escapes in an mda option could open a securityhole, because they pass text manipulable by an attacker to a shellcommand. Potential shell characters are replaced by '_' beforeexecution. The hole is further reduced by the fact that fetchmailtemporarily discards any set-uid privileges it may have while running theMDA. For maximum safety, however, do not use an mda command containing%F or %T when fetchmail is run from the root account itself.

Fetchmail's method of sending bounces due to errors or spam-blocking andspam bounces requires that port 25 of localhost be available for sendingmail via SMTP.

If you modify ~/.fetchmailrc while a background instance isrunning and break the syntax, the background instance will die silently.Unfortunately, it cannot die noisily because we do not yet know whethersyslog should be enabled. On some systems, fetchmail dies quietly evenif there is no syntax error; this seems to have something to do withbuggy terminal ioctl code in the kernel.

The -f~- option (reading a configuration from stdin) is incompatiblewith the plugin option.

Interactively entered passwords are truncated after 63 characters. Ifyou really need to use a longer password, you will have to use aconfiguration file.

A backslash as the last character of a configuration file will beflagged as a syntax error rather than ignored.

The BSMTP error handling is virtually nonexistent and may leave brokenmessages behind.

Send comments, bug reports, gripes, and the like to thefetchmail-devel list

Anfetchmail FAQ (in HTML form)is available at the fetchmail home page, it should also accompany yourinstallation.

 

AUTHOR

Fetchmail is currently maintained by Matthias Andree and Rob Funk withmajor assistance from Sunil Shetye (for code) and Rob MacGregor (for themailing lists).

Most of the code is fromEric S. RaymondToo many other people to name here have contributed code and patches.

This program is descended from and replacespopclient,byCarl Harristhe internals have become quite different, but some of its interfacedesign is directly traceable to that ancestral program.

This manual page has been improved by Matthias Andree, R. HannesBeinert, and Héctor García.

 

SEE ALSO

README,README.SSL,README.SSL-SERVER,The Fetchmail FAQmutt(1),elm(1),mail(1),sendmail(8),popd(8),imapd(8),netrc(5),the fetchmail home page(alternative URI)the maildrop home page. 

APPLICABLE STANDARDS

Note that this list is just a collection of references and not astatement as to the actual protocol conformance or requirements infetchmail.

SMTP/ESMTP:

RFC 821, RFC 2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC 1985,RFC 2554.

mail:

RFC 822, RFC 2822, RFC 1123, RFC 1892, RFC 1894.

POP3:

RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1734, RFC 1939, RFC 1957,RFC 2195, RFC 2449.

IMAP2/IMAP2BIS:

RFC 1176, RFC 1732.

IMAP4/IMAP4rev1:

RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC 2177,RFC 2683.

ETRN:

RFC 1985.

ODMR/ATRN:

RFC 2645.

LMTP:

RFC 2033.

GSSAPI:

RFC 1508, RFC 1734,Generic Security Service Application Program Interface (GSSAPI)/Kerberos/SimpleAuthentication and Security Layer (SASL) Service Names

TLS:

RFC 2595.

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Index

NAME

SYNOPSIS

DESCRIPTION

DEPRECATION AND CRYPTOGRAPHIC SECURITY WARNINGS

SUPPORT, TROUBLESHOOTING

QUICKSTART

TLS (SSL) QUICKSTART

CONCEPTS

PREFACE ON THIS MANUAL

GENERAL OPERATION

General Options

Disposal Options

Protocol and Query Options

Delivery Control Options

Resource Limit Control Options

Authentication Options

Miscellaneous Options

Removed Options

USER AUTHENTICATION AND ENCRYPTION

Using passwordeval

Using netrc files

Secure Socket Layers (SSL) and Transport Layer Security (TLS)

RETR or TOP

ALTERNATE AUTHENTICATION FORMS/METHODS

ESMTP AUTH

DAEMON MODE

Introducing the daemon mode

Starting the daemon mode

Awakening the background daemon

Terminating the background daemon

Useful options for daemon mode

ADMINISTRATIVE OPTIONS

RETRIEVAL FAILURE MODES

SPAM FILTERING

SMTP/ESMTP ERROR HANDLING

THE RUN CONTROL FILE

Run Control Syntax

Poll versus Skip

KEYWORD/OPTION SUMMARY

Keywords Not Corresponding To Option Switches

Singledrop versus Multidrop options

Miscellaneous Run Control Options

DEBUGGING FETCHMAIL

Fetchmail crashing

Enabling fetchmail core dumps

INTERACTION WITH RFC 822

CONFIGURATION EXAMPLES

THE USE AND ABUSE OF MULTIDROP MAILBOXES

Header versus Envelope addresses

Good Ways To Use Multidrop Mailboxes

Bad Ways To Abuse Multidrop Mailboxes

Speeding Up Multidrop Checking

Duplicate suppression on multidrop

SOCKS

EXIT CODES

FILES

ENVIRONMENT

SIGNALS

BUGS, LIMITATIONS, AND KNOWN PROBLEMS

AUTHOR

SEE ALSO

APPLICABLE STANDARDS

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This document was created byman2html,using the manual pages.