MAN page from RedHat Other fetchmail-6.2.2-1.i386.rpm

fetchmail

Section: User Commands (1)
Index 

NAME

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

 

SYNOPSIS

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

 

DESCRIPTION

fetchmailis a mail-retrieval and forwarding utility; it fetches mail fromremote mailservers and forwards it to your local (client) machine'sdelivery system. You can then handle the retrieved mail using normalmail user agents such as mutt(1), elm(1) or Mail(1).The fetchmail utility can be run in a daemon mode to repeatedlypoll one or more systems at a specified interval.

Thefetchmailprogram can gather mail from servers supporting any of the commonmail-retrieval protocols: POP2, POP3, IMAP2bis, IMAP4, and IMAPrev1.It can also use the ESMTP ETRN extension and ODMR. (The RFCs describing allthese protocols are listed at the end of this manual page.)

Whilefetchmailis primarily intended to be used over on-demand TCP/IP links (such asSLIP or PPP connections), it may also be useful as a message transferagent for sites which refuse for security reasons to permit(sender-initiated) SMTP transactions with sendmail.

As each message is retrieved fetchmail normally delivers it via SMTP toport 25 on the machine it is running on (localhost), just as though itwere being passed in over a normal TCP/IP link. The mail will then bedelivered locally via your system's MDA (Mail Delivery Agent, usuallysendmail(8) but your system may use a different one suchas smail, mmdf, exim, or qmail). All thedelivery-control mechanisms (such as .forward files) normallyavailable through your system MDA and local delivery agents willtherefore work automatically.

If no port 25 listener is available, but your fetchmail configurationwas told about a reliable local MDA, it will use that MDA for localdelivery instead. At build time, fetchmail normally looks forexecutableprocmail(1)and sendmail(1)binaries.

If the programfetchmailconfis available, it will assist you in setting up and editing afetchmailrc configuration. It runs under X and requires that thelanguage Python and the Tk toolkit be present on your system. Ifyou are first setting up fetchmail for single-user mode, it isrecommended that you use Novice mode. Expert mode providescomplete control of fetchmail configuration, including themultidrop features. In either case, the `Autoprobe' buttonwill tell you the most capable protocol a given mailserversupports, and warn you of potential problems with that server.

 

GENERAL OPERATION

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

Each server name that you specify following the options on thecommand line will be queried. If you don't specify any serverson the command line, each `poll' entry in your ~/.fetchmailrcfile will be queried.

To facilitate the use offetchmailin scripts and pipelines, it returns an appropriate exit code upon termination -- see EXIT CODES below.

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 .fetchmailrcfile.

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

General Options

-V | --version

Displays the version information for your copy of fetchmail.No mail fetch is performed.Instead, for each server specified, all the option informationthat would be computed iffetchmailwere connecting to that server is displayed. Any non-printables inpasswords or other string names are shown as backslashed C-likeescape sequences. This option is useful for verifying that youroptions 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). Itdoesn't play well with queries to multiple sites, and doesn't workwith ETRN or ODMR. It will return a false positive if you leave read butundeleted mail in your server mailbox and your fetch protocol can'ttell kept messages from new ones. This means it will work with IMAP,not work with POP2, and may occasionally flake out under POP3.

-s | --silent

Silent mode. Suppresses all progress/status messages that arenormally echoed to standard error 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 mailserver are echoed to stdout. Overrides --silent.Doubling this option (-v -v) causes extra diagnostic informationto be printed.

 

Disposal Options

-a | --all

(Keyword: fetchall)Retrieve both old (seen) and new messages from the mailserver. 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.Note that POP2 retrieval behaves as though --all is always on (seeRETRIEVAL FAILURE MODES below) and this option does not work with ETRNor ODMR.

-k | --keep

(Keyword: keep)Keep retrieved messages on the remote mailserver. Normally, messages are deleted from the folder on the mailserver after they have been retrieved.Specifying the keep option causes retrieved messages to remain in your folder on themailserver. This option does not work with ETRN or ODMR.

-K | --nokeep

(Keyword: nokeep)Delete retrieved messages from the remote mailserver. 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.

-F | --flush

POP3/IMAP only. Delete old (previously retrieved) messages from the mailserverbefore retrieving new messages. This option does not work with ETRN orODMR. In combination with the --limit option, --flush can be used to delete oversized messages waiting on the server.Warning: if your local MTA hangs and fetchmail is aborted, the nexttime you run fetchmail, it will delete mail that was never delivered to you.What you probably want is the default setting: if you don't specify `-k', thenfetchmail will automatically delete messages after successful delivery.

 

Protocol and Query Options

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

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

AUTO

Tries IMAP, POP3, and POP2 (skipping any of these for which supporthas not been compiled in).

POP2

Post Office Protocol 2

POP3

Post Office Protocol 3

APOP

Use POP3 with old-fashioned MD5-challenge authentication.

RPOP

Use POP3 with RPOP authentication.

KPOP

Use POP3 with Kerberos V4 authentication on port 1109.

SDPS

Use POP3 with Demon Internet's SDPS extensions.

IMAP

IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail autodetects their capabilities).

ETRN

Use the ESMTP ETRN option.

ODMR

Use the 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.

-U | --uidl

(Keyword: uidl)Force UIDL use (effective only with POP3). Force client-side trackingof `newness' of messages (UIDL stands for ``unique ID listing'' and isdescribed in RFC1725). Use with `keep' to use a mailbox as a babynews drop for a group of users. The fact that seen messages are skippedis logged, unless error logging is done through syslog while running indaemon mode.

-P <portnumber> | --port <portnumber>

(Keyword: port)The port option permits you to specify a TCP/IP port to connect on. This option will seldom be necessary as all the supported protocols havewell-established default port numbers.

--principal <principal>

(Keyword: principal)The principal option permits you to specify a service principal formutual authentication. This is applicable to POP3 or IMAP with Kerberosauthentication.

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

(Keyword: timeout)The timeout option allows you to set a server-nonresponsetimeout in seconds. If a mailserver does not send a greeting messageor respond to commands for the given number of seconds,fetchmail will hang up on it. Without such a timeoutfetchmail might hang up indefinitely trying to fetch mail from adown host. This would be particularly annoying for a fetchmailrunning in background. There is a default timeout which fetchmail -Vwill report. If a given connection receives too many timeouts in succession, fetchmail will consider it wedged and stop retrying,the calling user will be notified by email if this happens.

--plugin <command>

(Keyword: plugin) The plugin option allows you to use an externalprogram to establish the TCP connection. This is useful if you wantto use socks, SSL, ssh, or need some special firewalling setup. Theprogram will be looked up in $PATH and can optionally be passed thehostname and port as arguments using "%h" and "%p" respectively (notethat the interpolation logic is rather primitive, and these token 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 (which will probably not need it, so it has been separatedfrom plugin).

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

(Keyword: folder[s])Causes a specified non-default mail folder on the mailserver (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 fetchail to poll trace information in the form `polling %saccount %s' to the Received line it generates, where the %s parts arereplaced by the user's remote name and the poll label (the Receivedheader also normally includes the server's truename). This can beused to facilate mail filtering based on the account it is beingreceived from.

--ssl

(Keyword: ssl)Causes the connection to the mail server to be encrypted via SSL. Connectto the server using the specified base protocol over a connection securedby SSL. SSL support must be present at the server. If no port isspecified, the connection is attempted to the well known port of the SSLversion of the base protocol. This is generally a different port than theport used by the base protocol. For IMAP, this is port 143 for the clearprotocol and port 993 for the SSL secured protocol.

--sslcert <name>

(Keyword: sslcert)Specifies the file name of the client side public SSL certificate. SomeSSL encrypted servers may require client side keys and certificates forauthentication. In most cases, this is optional. This specifiesthe location of the public key certificate to be presented to the serverat the time the SSL session is established. It is not required (but maybe provided) if the server does not require it. Some servers mayrequire it, some servers may request it but not require it, and someservers may not request it at all. It may be the same fileas the private key (combined key and certificate file) but this is notrecommended.

--sslkey <name>

(Keyword: sslkey)Specifies the file name of the client side private SSL key. Some SSLencrypted servers may 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. Some servers mayrequire it, some servers may request it but not require it, and someservers may not request it at all. 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 beprompted for at the time just prior to establishing the session to theserver. This can cause some complications in daemon mode.

--sslproto <name>

(Keyword: sslproto)Forces an ssl protocol. Possible values are `ssl2', `ssl3' and`tls1'. Try this if the default handshake does not work for your server.

--sslcertck

(Keyword: sslcertck)Causes fetchmail to strictly check the server certificate against a set oflocal trusted certificates (see the sslcertpath option). If the servercertificate is not signed by one of the trusted ones (directly or indirectly),the SSL connection will fail. This checking should prevent man-in-the-middleattacks against the SSL connection. Note that CRLs are seemingly not currentlysupported by OpenSSL in certificate verification! Your system clock shouldbe reasonably accurate when using this option!

--sslcertpath <directory>

(Keyword: sslcertpath)Sets the directory fetchmail uses to look up local certificates. The defaultis your OpenSSL default one. The directory must be hashed as OpenSSL expectsit - every time you add or modify a certificate in the directory, you needto use the c_rehash tool (which comes with OpenSSL in the tools/subdirectory).

--sslfingerprint

(Keyword: sslfingerprint)Specify the fingerprint of the server key (an MD5 hash of the key) inhexadecimal notation with colons separating groups of two digits. The letterhex digits must be in upper case. This is the default format OpenSSL uses,and the one fetchmail uses to report the fingerprint when an SSL connectionis established. When this is specified, fetchmail will compare the server keyfingerprint with the given one, and the connection will fail if they do notmatch. This can be used to prevent man-in-the-middle attacks.

 

Delivery Control Options

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

(Keyword: smtp[host])Specify a hunt list of hosts to forward mail to (one or morehostnames, comma-separated). Hosts are tried in list order; the firstone that is up becomes the forwarding target for the current run.Normally, `localhost' is added to the end of the list as an invisibledefault. However, when using Kerberos authentication, the FQDN of themachine running fetchmail is added to the end of the list as aninvisible default. Each hostname may have a port number following thehost name. The port number is separated from the host name by aslash; the default port is 25 (or ``smtp'' under IPv6). If youspecify an absolute pathname (beginning with a /), it will beinterpreted as the name of a UNIX socket accepting LMTP 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.

--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 addressesin RCPT TO lines shipped to SMTP. The name of the SMTP server (asspecified by --smtphost, or defaulted to "localhost") is used whenthis is not specified.

--smtpname <userAATTdomain>

(Keyword: smtpname) Specify the domain and user to be put in RCPT TO lines shipped to SMTP.The default user is the current local user.

-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.

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

(Keyword: mda)You can force mail to be passed to an MDA directly (rather thanforwarded to port 25) with the --mda or -m option. To avoid losingmail, use this option only with MDAs like procmail or sendmail thatreturn a nonzero status on disk-full and other resource-exhaustionerrors; the nonzero status tells fetchmail that delivery failed andprevents the message from being deleted off the server. Iffetchmail is running as root, it sets its userid to that of thetarget user while delivering mail through an MDA. Some possible MDAsare "/usr/sbin/sendmail -i -f %F %T", "/usr/bin/deliver" and"/usr/bin/procmail -d %T" (but the latter is usually redundant as it'swhat SMTP listeners normally forward to). Local delivery addresseswill be inserted into the MDA command wherever you place a %T; themail message's From address will be inserted where you place an %F.Do not use an MDA invocation like "sendmail -i -t" thatdispatches on the contents of To/Cc/Bcc, it will create mail loops andbring the just wrath of many postmasters down upon your head.

--lmtp

(Keyword: lmtp)Cause delivery via LMTP (Local Mail Transfer Protocol). A serviceport must be explicitly specified (with a slash suffix) on eachhost in the smtphost hunt list if this option is selected; thedefault port 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 mailto be written to standard output. Note that fetchmail'sreconstruction of MAIL FROM and RCPT TO lines is not guaranteedcorrect; the caveats discussed under THE USE AND ABUSE OF MULTIDROPMAILBOXES below apply.

 

Resource Limit Control Options

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

(Keyword: limit) Takes a maximum octet size argument. Messages largerthan this size will not be fetched and will be left on the server (inforeground sessions, the progress messages will note that they are"oversized"). If the fetch protocol permits (in particular, underIMAP or POP3 without the fetchall option) the message will not bemarked 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 --flush, it can be used to delete oversized messageswaiting on a server. In daemon mode, oversize notifications aremailed to the calling user (see the --warnings option). This optiondoes not work with ETRN or ODMR.

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

(Keyword: warnings)Takes an interval in seconds. When you callfetchmailwith 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 the first poll thatthe oversized message is detected. Thereafter, renotification 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.

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

(keyword: expunge) Arrange for deletions to be made final after a given number ofmessages. Under POP2 or 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 multiplesubsessions, sending QUIT after each sub-session. This is a gooddefense against line drops on POP3 servers that do not do theequivalent of a QUIT on hangup. Under IMAP,fetchmailnormally issues an EXPUNGE command after each deletion in order toforce the deletion to be done immediately. This is safest when yourconnection to the server is flaky and expensive, as it avoidsresending 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 tellsfetchmailto only issue expunges on every Nth delete. An argument of zerosuppresses expunges entirely (so no expunges at all will be done untilthe end of run). This option does not work with ETRN or ODMR.

 

Authentication Options

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

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

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

(Keyword: interface)Require that a specific interface device be up and have a specific localor remote IP address (or range) before polling. Frequentlyfetchmailis used over a transient point-to-point TCP/IP link established directlyto a mailserver via SLIP or PPP. That is a relatively secure channel.But when other TCP/IP routes to the mailserver 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 below for FreeBSD specific information.

-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 interfaceoptions to work for non root users under FreeBSD, the fetchmail binarymust be installed SGID kmem. This would be a security hole, butfetchmail runs with the effective GID set to that of the kmem grouponlywhen interface data is being collected.

--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' and `kerberos' (or, forexcruciating exactness, `kerberos_v4'), gssapi,cram-md5, otp, ntlm, and ssh. When any (thedefault) is specified, fetchmail tries first methods that don'trequire a password (GSSAPI, KERBEROS_IV); then it looks for methodsthat mask your password (CRAM-MD5, X-OTP, NTLM); and only if the serverdoesn't support any of those will it ship your password en clair.Other values may be used to force various authentication methods(ssh suppresses authentication). Any value other thanpassword, cram-md5, ntlm or otp suppresses fetchmail'snormal inquiry for a password. Specify ssh when you are usingan end-to-end secure connection such as an ssh tunnel; specifygssapi or kerberos_v4 if you are using a protocol variantthat employs GSSAPI or K4. Choosing KPOP protocol automaticallyselects Kerberos authentication. This option does not work with ETRN.

 

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 0600 (u=rw,g=,o=) orelse be /dev/null.

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

(Keyword: idfile)Specify an alternate name for the .fetchids file used to save POP3UIDs.

-n | --norewrite

(Keyword: no rewrite)Normally,fetchmailedits RFC-822 address headers (To, From, Cc, Bcc, and Reply-To) infetched mail so that any mail IDs local to the server are expanded tofull addresses (@ and the mailserver hostname are appended). This enables replies on the client to get addressed correctly (otherwise yourmailer might think they should be addressed to local users on theclient machine!). This option disables the rewrite. (This option isprovided to pacify people who are paranoid about having an MTA editmail headers and want to know they can prevent it, but it is generallynot a good idea to actually turn off rewrite.)When using ETRN or ODMR, the rewrite option is ineffective.

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

(Keyword: envelope)This option changes the header fetchmailassumes will carry a copy of the mail's envelope address. Normallythis is `X-Envelope-To' but as this header is not standard, practicevaries. See the discussion of multidrop address handling below. As aspecial case, `envelope "Received"' enables parsing of sendmail-styleReceived lines. This is the default, and it should not be necessaryunless you have globally disabled Received parsing with `no envelope'in the .fetchmailrc file.

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

(Keyword: qvirtual)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 using fetchmailto collect the mail for an entire domain and your ISP (or your mailredirection 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 hostname 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 a`Delivered-To:' line of the form:

Delivered-To: mbox-userstr-usernameAATTuserhost.userdom.dom.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 ~/.fetchmailrcfile, interpret any command-line options specified, and dump aconfiguration report to standard output. The configuration report isa data structure assignment in the language Python. This optionis meant to be used with an interactive ~/.fetchmailrceditor like fetchmailconf,written in Python.

 

USER AUTHENTICATION AND ENCRYPTION

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

If the mailserver is a Unix machine on which you have an ordinary user account, your regular login name and password are used with fetchmail.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 fetchmailis to prompt you for your mailserver password before the connection isestablished. This is the safest way to use fetchmailand ensures that your password will not be compromised. You may also specifyyour password in your~/.fetchmailrcfile. This is convenient when using fetchmailin daemon mode or with scripts.

If you do not specify a password, andfetchmailcannot extract one from your~/.fetchmailrcfile, it will look for a ~/.netrcfile in your home directory before requesting one interactively; if anentry matching the mailserver 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. See theftp(1)man page for details of the syntax of the~/.netrcfile. (This feature may allow you to avoid duplicating passwordinformation in more than one file.)

On mailservers that do not provide ordinary user accounts, your user-id and password are usually assigned by the server administrator when you apply for a mailbox on the server. Contact your server administrator if you don't know the correct user-id and password for your mailbox account.

Early versions of POP3 (RFC1081, RFC1225) supported a crude form ofindependent authentication using therhostsfile on the mailserver side. Under this RPOP variant, a fixedper-user ID equivalent to a password was sent in clear over a link toa reserved port, with the command RPOP rather than PASS to alert theserver that it should do special checking. RPOP is supportedbyfetchmail(you can specify `protocol RPOP' to have the program send `RPOP'rather than `PASS') but its use is strongly discouraged. Thisfacility was vulnerable to spoofing and was withdrawn in RFC1460.

RFC1460 introduced APOP authentication. In this variant of POP3,you register an APOP password on your server host (the programto do this with on the server is probably called popauth(8)). Youput the same password in your ~/.fetchmailrcfile. Each time fetchmaillogs in, it sends a cryptographically secure hash of your password andthe server greeting time to the server, which can verify it bychecking its authorization database.

If your fetchmail was built with Kerberos support and you specify Kerberos authentication (either with --auth or the .fetchmailrcoption authenticate kerberos_v4) it will try to get a Kerberosticket from the mailserver at the start of each query. Note: ifeither the pollnane or via name is `hesiod', fetchmail will try to useHesiod to look up the mailserver.

If you use POP3 or IMAP with GSSAPI authentication, fetchmail willexpect the server to have RFC1731- or RFC1734-conformant GSSAPIcapability, and will use it. Currently this has only been tested overKerberos V, so you're 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 `ssh' on thatsite entry 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.

Compuserve's RPA authentication (similar to APOP) is supported. If youcompile in the support, fetchmail will try to perform an RPA pass-phraseauthentication instead of sending over the password en clair if itdetects "@compuserve.com" in the hostname.

If you are using IMAP, Microsoft's NTLM authentication (used by MicrosoftExchange) is supported. If you compile in the support, fetchmailwill try to perform an NTLM authentication (instead of sending over thepassword en clair) whenever the server returns AUTH=NTLM in itscapability response. Specify a user option value that looks like`userAATTdomain': the part to the left of the @ will be passed as theusername and the part to the right as the NTLM domain.

If you are using IPsec, the -T (--netsec) option can be used to passan IP security request to be used when outgoing IP connections areinitialized. You can also do this using the `netsec' server optionin the .fetchmailrc file. In either case, the option value is astring in the format accepted by the net_security_strtorequest() function of the inet6_apps library.

You can access SSL encrypted services by specifying the --ssl option.You can also do this using the "ssl" server option in the .fetchmailrcfile. With SSL encryption enabled, queries are initiated over a connectionafter negotiating an SSL session. Some services, such as POP3 and IMAP,have different well known ports defined for the SSL encrypted services.The encrypted ports will be selected automatically when SSL is enabled andno explicit port is specified.

When connecting to an SSL encrypted server, the server presents a certificateto the client for validation. The certificate is checked to verify thatthe common name in the certificate matches the name of the server beingcontacted and that the effective and expiration dates in the certificateindicate that it is currently valid. If any of these checks fail, a warningmessage is printed, but the connection continues. The server certificatedoes not need to be signed by any specific Certifying Authority and maybe a "self-signed" certificate.

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 doesn't help against anactive attacker. It's 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 as dsniff,http://www.monkey.org/~dugsong/dsniff/). Use of an ssh tunnel (seebelow for some examples) is preferable if you care seriously about thesecurity of your mailbox.

fetchmailalso supports authentication to the ESMTP server on the client sideaccording to RFC 2554. You can specify a name/password pair to beused with the keywords `esmtpname' and `esmtppassword'; the formerdefaults to the username of the calling user.

 

DAEMON MODE

The --daemon <interval>or-d <interval>option runs fetchmailin daemon mode. You must specify a numeric argument which is apolling interval in seconds.

In daemon mode, fetchmailputs itself in background and runs forever, querying each specifiedhost and then sleeping for the given polling interval.

Simply invoking

fetchmail -d 900

will, therefore, poll all the hosts described in your ~/.fetchmailrcfile (except those explicitly excluded with the `skip' verb) onceevery fifteen minutes.

It is possible to set a polling interval in your~/.fetchmailrcfile by saying `set daemon <interval>', where <interval> is aninteger number of seconds. If you do this, fetchmail will alwaysstart in daemon mode unless you override it with the command-lineoption --daemon 0 or -d0.

Only one daemon process is permitted per user; in daemon mode,fetchmailmakes a per-user lockfile to guarantee this.

Normally, calling fetchmail with a daemon in the background sends awakeup signal to the daemon, forcing it to poll mailserversimmediately. (The wakeup signal is SIGHUP if fetchmail is running asroot, SIGUSR1 otherwise.) The wakeup action also clears any `wedged'flags indicating that connections have wedged due to failed authentication or multiple timeouts.

The option--quitwill kill a running daemon process instead of waking it up (if thereis no such process, fetchmailnotifies you). If the --quit option is the only command-line option,that's all there is to it.

The quit option may also be mixed with other command-line options; itseffect is to kill any running daemon before doing what the otheroptions specify in combination with the rc file.

The-L <filename>or--logfile <filename>option (keyword: set logfile) allows you to redirect status messagesemitted while detached into a specified logfile (follow theoption with the logfile name). The logfile is opened for append, soprevious messages aren't deleted. This is primarily useful fordebugging configurations.

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 of syslog(3),assuming it's turned on in the ~/.fetchmailrc file, or that the-Lor--logfile <file>option was used.

The -Nor --nodetach option suppresses backgrounding and detachment of thedaemon process from its control terminal. This is primarily usefulfor debugging. Note that this also causes the logfile option to beignored (though perhaps it shouldn't).

Note that while running in daemon mode polling a POP2 or 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 mailserver) but not deliveredlocally due to some transient error, it will be re-fetched during thenext poll cycle. (The IMAP logic doesn't delete messages untilthey're delivered, so this problem does not arise.)

If you touch or change the ~/.fetchmailrc file while fetchmail is running in daemon mode, this will be detected at the beginning of the next poll cycle. When a changed~/.fetchmailrc is detected, fetchmail rereads it and restarts from scratch (usingexec(2); no state information is retained in the new instance). Note alsothat if you break the~/.fetchmailrc file's syntax, the new instance will softly and silently vanish awayon 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. Normally this is just the user who invoked fetchmail.If the invoking user is root, then the default of this option isthe user `postmaster'. Setting postmaster to the empty string causessuch mail to be discarded.

The--nobounceoption suppresses the normal action of bouncing errors back to the sender in an RFC1894-conformant error message. If nobounce is on, themessage will go to the postmaster instead.

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 themailserver host.

The --showdotsoption (keyword: set showdots) forces fetchmail to show progress dotseven if the current tty is not stdout (for example logfiles).Starting with fetchmail version 5.3.0, progress dots are only shown on stdout by default.

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 mailservers 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.The well-knownprocmail(1)program is like this; so are most programs designed as mail transportagents, such as sendmail(1),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've already read on theserver are being fetched (and deleted) even when you don't specify--all. There are several reasons this can happen.

One could be that you're using POP2. The POP2 protocol includes norepresentation of `new' or `old' state in messages, so fetchmailmust treat all messages as new all the time. But POP2 is obsolete, sothis is unlikely.

Under POP3, blame RFC1725. That version of the POP3 protocolspecification removed the LAST command, and some POP servers follow it(you can verify this by invoking fetchmail -v to the mailserverand watching the response to LAST early in the query). Thefetchmail code tries to compensate by using POP3's UID feature,storing the identifiers of messages seen in each session until thenext session, in the .fetchids file. But this doesn't trackmessages seen with other clients, or read directly with a mailer onthe host but not deleted afterward. A better solution would be toswitch to IMAP.

Another 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. The only real fix for this problem is to switch to IMAP.

Yet another POP3 problem is that if they can't make tempfiles 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. Under Unix, it counts onyour IMAP server to notice the BSD-style Status flags set by mail useragents and set the \Seen flag from them when appropriate. All UnixIMAP servers we know of do this, though it's not specified by the IMAPRFCs. If you ever trip over a server that doesn't, the symptom willbe that messages you have already read on your host will look new tothe server. In this (unlikely) case, only messages you fetched withfetchmail --keep will 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 of sendmailreturn an error code of 571. This return valueis blessed by RFC1893 as "Delivery not authorized, message refused".

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.

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

Return codes which fetchmailtreats 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 ofmultidropped 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 won't pay for downloading spam message bodies.

By default, the list of antispam responses is empty.

If the spambounce option is on, mail that is spam-blockedtriggers an RFC1892 bounce message informing the originator that we donot accept mail from it.

 

SMTP/ESMTP ERROR HANDLING

Besides the spam-blocking described above, fetchmail takes specialactions on the following SMTP/ESMTP error responses

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. Don't even try to sendbounce-mail to the originator.

Other errors trigger bounce mail back to the originator.

 

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, when --version is not onyour ~/.fetchmailrc may not have more than 0600 (u=rw,g=,o=) permissions;fetchmailwill complain and exit otherwise.

You may read the .fetchmailrc file as a list of commands to be executed when fetchmailis 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). An unquotedstring is any whitespace-delimited token that is neither numeric, stringquoted nor contains the special characters `,', `;', `:', or `='.

Any amount of whitespace separates tokens in server entries, but isotherwise ignored. You may use standard C-style escapes (\n, \t,\b, octal, and hex) to embed non-printable characters or stringdelimiters in strings.

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 descriptions. Note: the most common cause of syntaxerrors is mixing up user and server options.

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're ignored, but but can make entries mucheasier to read at a glance. The punctuation characters ':', ';' and',' are also ignored.

 

Poll vs. Skip

The `poll' verb tells fetchmail to query this host when it is run withno arguments. The `skip' verb tellsfetchmail not 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 command-lineoptions are followed by `-' and the appropriate option letter.

Here are the legal global options:

Keyword	Opt	Function
set daemon		Set a background poll interval in seconds
set postmaster		Give the name of the last-resort mail recipient
set no bouncemail		Direct error mail to postmaster rather than sender
set no spambounce		Send spam bounces
set logfile		Name of a file to dump error and status messages to
set idfile		Name of the file to store UID lists in
set syslog		Do error logging through syslog(3).
set no syslog		Turn off error logging through syslog(3).
set properties		String value is ignored by fetchmail (may be used by extension scripts)

Here are the legal server options:

Keyword	Opt	Function
via		Specify DNS name of mailserver, overriding poll name
proto[col]	-p	Specify protocol (case insensitive):POP2, POP3, IMAP, APOP, KPOP
local[domains]		Specify domain(s) to be regarded as local
port	-P	Specify TCP/IP service port
auth[enticate]		Set authentication type (default `any')
timeout	-t	Server inactivity timeout in seconds (default 300)
envelope	-E	Specify envelope-address header name
no envelope		Disable looking for envelope address
qvirtual	-Q	Qmail virtual domain prefix to remove from user name
aka		Specify alternate DNS names of mailserver
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		Enable DNS lookup for multidrop (default)
no dns		Disable DNS lookup for multidrop
checkalias		Do comparison by IP address for multidrop
no checkalias		Do comparison by name for multidrop (default)
uidl	-U	Force POP3 to use client-side UIDLs
no uidl		Turn off POP3 use of client-side UIDLs (default)
interval		Only check this site every N poll cycles; N is a numeric argument.
netsec		Pass in IPsec security option request.
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.

Here are the legal user options:

Keyword	Opt	Function
user[name]	-u	Set remote user name (local user name if name followed by `here')
is		Connect local and remote user names
to		Connect local and remote user names
pass[word]		Specify remote account password
ssl		Connect to server over the specified base protocol using SSL encryption
sslcert		Specify file for client side public SSL certificate
sslkey		Specify file for client side private SSL key
sslproto		Force ssl protocol for connection
folder	-r	Specify remote folder to query
smtphost	-S	Specify smtp host(s) to forward to
fetchdomains		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	Don't delete seen messages from server
flush	-F	Flush all seen 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)
no keep	-K	Delete seen messages from server (default)
no flush		Don't flush all seen messages before querying (default)
no fetchall		Retrieve only new messages (default)
no rewrite		Don't rewrite headers
no stripcr		Don't strip carriage returns (default)
no forcecr		Don't force carriage returns at EOL (default)
no pass8bits		Don't force BODY=8BITMIME to ESMTP listener (default)
no dropstatus		Don't drop Status headers (default)
no dropdelivered