fetchmail - Unix, Linux Command (2024)

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

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

fetchmailconf

fetchmail is 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.

Thefetchmail program can gather mail from servers supporting any of the commonmail-retrieval protocols: POP2 (legacy, to be removed from futurerelease), 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.)

Whilefetchmail is 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.

Iffetchmail is used with a POP or an IMAP server, it has two fundamental modes ofoperation for each user account from which it retrieves mail:singledrop- and multidrop-mode. In singledrop-mode,fetchmail assumes that all messages in the user’s account are intended for a singlerecipient. An individual mail message will not be inspected for recipientinformation, rather, the identity of the recipient will either default tothe local user currently executing fetchmail,or else will need to be explicitly specified in the configuration file.Singledrop-mode is used when the fetchmailrc configuration contains atmost a single local user specification for a given server account.

With multidrop-mode,fetchmail is not able to assume that there is only a single recipient, but ratherthat the mail server account actually contains mail intended for anynumber of different recipients. Therefore,fetchmail must attempt to deduce the proper "envelope recipient" from the mailheaders of each message. In this mode of operation,fetchmail almost resembles an MTA, however it is important to note that neitherthe POP nor IMAP protocols were intended for use in this fashion, andhence envelope information is often not directly available. Instead,fetchmail must resort to a process of informed guess-work in an attempt todiscover the true envelope recipient of a message, unless the ISP storesthe envelope information in some header (not all do). Even if thisinformation is present in the headers, the process canbe error-prone and is dependent upon the specific mail server usedfor mail retrieval. Multidrop-mode is used when more than one localuser is specified for a particular server account in the configurationfile. Note that the forgoing discussion of singledrop- andmultidrop-modes does not apply to the ESMTP ETRN or ODMR retrievalmethods, since they are based upon the SMTP protocol whichspecifically provides the envelope recipient to fetchmail.

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. fetchmail providesthe SMTP server with an envelope recipient derived in the manner describedpreviously. 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, postfix, 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.

If the programfetchmailconf is available, it will assist you in setting up and editing afetchmailrc configuration. It runs under the X window system andrequires that the language Python and the Tk toolkit be present on yoursystem. If you are first setting up fetchmail for single-user mode, itis recommended that you use Novice mode. Expert mode provides completecontrol of fetchmail configuration, including the multidrop features.In either case, the ’Autoprobe’ button will tell you the most capableprotocol a given mailserver supports, and warn you of potential problemswith that server.

The behavior offetchmail is 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~/.fetchmailrc declarations.

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~/.fetchmailrc file will be queried.

To facilitate the use offetchmail in scripts and pipelines, it returns an appropriate exit code upontermination -- 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.fetchmailrc file.

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

General Options

Disposal Options

Protocol and Query Options

openssl x509 -in cert.pem -noout -md5 -fingerprint

Delivery Control Options

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

Resource Limit Control Options

Authentication Options

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

Miscellaneous Options

Removed Options

All modes except ETRN require authentication of the client to the server.Normal user authentication infetchmail is very much like the authentication mechanism offtp(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 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-u option -- 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-u option. e.g. if your login name is ’jsmith’ on a machine named ’mailgrunt’,you would startfetchmail as follows:

The default behavior offetchmail is to prompt you for your mailserver password before the connection isestablished. This is the safest way to usefetchmail and ensures that your password will not be compromised. You may also specifyyour password in your~/.fetchmailrc file. This is convenient when usingfetchmail in daemon mode or with scripts.

Using netrc files

If you do not specify a password, andfetchmail cannot extract one from your~/.fetchmailrc file, it will look for a~/.netrc file 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~/.netrc file. To show a practical example, a .netrc might look likethis:

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.

On mailservers 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 don’t knowthe correct user-id and password for your mailbox account.

Early versions of POP3 (RFC1081, RFC1225) supported a crude form ofindependent authentication using therhosts file 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, and supportwill be removed from a future fetchmail version. 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 (on some servers, theprogram to do this is called popauth(8)). You put the samepassword in your ~/.fetchmailrc file. Each time fetchmaillogs in, it sends an MD5 hash of your password and the server greetingtime to the server, which can verify it by checking its authorizationdatabase.

Note that APOP is no longer considered resistant againstman-in-the-middle attacks.

RETR or TOP

fetchmail makes some efforts to make the server believe messages had not beenretrieved, by using the TOP command with a large number of lines whenpossible. TOP is a command that retrieves the full header anda 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.fetchmail will also use the RETR command if "keep" is set and "uidl" is unset.Finally,fetchmail will use the RETR command on Maillennium POP3/PROXYservers (used by Comcast) to avoid a deliberate TOP misinterpretation inthis server that causes message corruption.

In all other cases,fetchmail will use the TOP command. This implies that in "keep" setups, "uidl"must be set if "TOP" is desired.

Note that this description is true for the current version of fetchmail, butthe behavior may change in future versions. In particular, fetchmail mayprefer the RETR command because the TOP command causes much grief onsome servers and is only optional.

If your fetchmail was built with Kerberos support and you specifyKerberos 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 pollname 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-conforming 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 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.

Compuserve’s RPA authentication 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’user@domain’: the part to the left of the @ will be passed as theusername and the part to the right as the NTLM domain.

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

You can access SSL encrypted services by specifying the --ssl option.You can also do this using the "ssl" user option in the .fetchmailrcfile. With SSL encryption enabled, queries are initiated over a connectionafter negotiating an SSL session, and the connection fails if SSL cannotbe negotiated. Some services, such as POP3 and IMAP, have differentwell known ports defined for the SSL encrypted services. The encryptedports will be selected automatically when SSL is enabled and no explicitport is specified. The --sslproto option can be used to select the SSLprotocols (default: v2 or v3). The --sslcertck command line orsslcertck run control file option should be used to force strictcertificate checking - see below.

If SSL is not configured, fetchmail will usually opportunistically try to useTLS. TLS can be enforced by using --sslproto "TLS1". TLSconnections use the same port as the unencrypted version of theprotocol and negotiate TLS via special parameter. The --sslcertckcommand line or sslcertck run control file option should be used toforce strict certificate checking - see below.

--sslcheck recommended: When connecting to an SSL or TLS 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. If the --sslcertck command line optionor sslcertck run control file option is used, fetchmail will insteadabort if any of these checks fail. Use of the sslcertck or --sslcertckoption is advised.

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://monkey.org/~dugsong/dsniff/). Use of strict certificate checkingwith a certification authority recognized by server and client, orperhaps of an SSH tunnel (see below for some examples) is preferable ifyou care seriously about the security of your mailbox and passwords.

ESMTP AUTH

fetchmail also 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.

Introducing the daemon mode

In daemon mode,fetchmail puts itself into the background and runs forever, querying eachspecified host and then sleeping for a given polling 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 in seconds.

Example: simply invoking

will, therefore, poll all the hosts described in your~/.fetchmailrc file (except those explicitly excluded with the ’skip’ verb) onceevery 15 minutes.

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 lockfile 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 aren’t 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 anyauthentication or multiple timeouts.

Terminating the background daemon

The option--quit will 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. 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 aren’t 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).

The--syslog option (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--nosyslog option turns off use ofsyslog(3),assuming it’s turned on in the~/.fetchmailrc file, or that the-L or--logfile <file> option was used.

The-N or--nodetach option suppresses backgrounding and detachment of thedaemon process from its control terminal. This is usefulfor debugging or when fetchmail runs as the child of a supervisorprocess such asinit(8)or Gerrit Pape’srunit. 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 detectedat 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 also that if you break the~/.fetchmailrc file’s syntax, the new instance will softly and silently vanish awayon startup.

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--nobounce behaves like the "set no bouncemail" global option, which see.

The--invisible option (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--showdots option (keyword: set showdots) forces fetchmail to show progress dotseven if the current tty is not stdout (for example logfiles).Fetchmail shows the dots by default when run in nodetach mode or whendaemon mode is not enabled.

By specifying the--tracepolls option, 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’.

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.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’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.

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 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. This isn’t the right thingto do, fetchmail should check the UIDVALIDITY and use UID, but itdoesn’t 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’s not specified by the IMAP RFCs. If you ever trip overa server that doesn’t, 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.

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 ofsendmail return 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 theexim MTA return 501 "Syntax error in parameters or arguments".

Thepostfix MTA 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 whichfetchmail treats as antispam responses and discardsthe message can be set with the ’antispam’ option. This is one of theonly three circ*mstance 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).

Iffetchmail is 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 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.

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

Other errors trigger bounce mail back to the originator. See also BUGS.

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 0600 (u=rw,g=,o=) permissions;fetchmail will 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 whenfetchmail is 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 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 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:

Here are the legal server options:

Here are the legal user options:

Remember that all user options must follow all server 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 sometime 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 themailserver 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 vs. Multidrop options

The ’is’ or ’to’ keywords associate the following local (client)name(s) (or server-name to client-name mappings separated by =) withthe mailserver 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 themailserver. 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,fetchmail never 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 hostname partsthat match your poll name or your ’via’, ’aka’ or ’localdomains’options, and usually also for hostname parts which DNS tells it arealiases of the mailserver. See the discussion of ’dns’, ’checkalias’,’localdomains’, and ’aka’ for details on how matching addresses arehandled.

If fetchmail cannot match any mailserver 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 mailserver username is recognizedattached to a matching hostname 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’re polled using an alias.When such a server is polled, checks to extract the envelope addressfail, andfetchmail reverts to delivery using the To/Cc/Bcc headers (See below’Header vs. Envelope addresses’).Specifying this option instructsfetchmail to retrieve all the IP addresses associated with both the poll nameand the name used by the remote MTA and to do a comparison of the IPaddresses. This comes in handy in situations where the remote serverundergoes frequent canonical name changes, that would otherwiserequire 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 through message headerslooking for names of the mailserver, pre-declaring common ones cansave it from having to do DNS lookups. Note: the names you giveas arguments to ’aka’ are matched as suffixes -- if you specify(say) ’aka netaxs.com’, this will match not just a hostnamenetaxs.com, but any hostname 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 timefetchmail establishes a mailserver 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 mailserverwill be aborted.

Similarly, the ’postconnect’ keyword similarly allows you to specify ashell command to be executed just after each time a mailserverconnection 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 it 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,fetchmail declares 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,fetchmail is 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 mailservers in order to avoid mail loops butmay get in your way if you try to "mirror" a mailserver 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 doesn’t 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) pop2 (or POP2) (legacy, to be removed from future release) pop3 (or POP3) sdps (or SDPS) imap (or IMAP) apop (or APOP) kpop (or KPOP)

Legal authentication types are ’any’, ’password’, ’kerberos’,’kerberos_v4’, ’kerberos_v5’ and ’gssapi’, ’cram-md5’, ’otp’, ’msn’(only for POP3), ’ntlm’, ’ssh’, ’external’ (only IMAP).The ’password’ type specifiesauthentication by normal transmission of a password (the password may beplain text or subject to protocol-specific encryption as in CRAM-MD5);’kerberos’ 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 V4authentication. 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. 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).

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. <http://www.bitwizard.nl/sig11/> may 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.

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 doesn’t contain an @ or !) Sender: (ignored if it doesn’t 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 doesn’t exist, the bounce messagewon’t 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 Received: header (or whichever one isspecified by the ’envelope’ option) to determine the localrecipient address. If the mail is addressed to more than one recipient,the Received line won’t contain any 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 don’t 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.)

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.

Basic format is:

 poll SERVERNAME protocol PROTOCOL username NAME password 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 pop2 user "John.Smith" pass "My^Hat"

Here’s a version of those two 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 pop2: user "John.Smith", with password "My^Hat", is "John.Smith" here;

This version is much easier to read and doesn’t cost significantlymore (parsing is done only once, at startup time).

If you need to include whitespace in a parameter string, enclose thestring in double quotes. Thus:

 poll mail.provider.net with proto pop3: user "jsmith" there has password "u can’t 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’s possible to specify more than one user per server (this is onlylikely to be useful when running fetchmail in daemon mode as root).The ’user’ keyword leads off a user description, and every user specificationin a multi-user entry must include it. Here’s 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’s 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 thatfetchmail, until version 6.3.4, did NOT allow full user@domain specifications here,these would never match. Fetchmail 6.3.5 and newer supportuser@domain specifications on the left-hand side of a user mapping.

Here’s an example of another kind of multidrop connection:

 poll pop.provider.net localdomains loonytoons.org toons.org: 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’joe@daffy.loonytoons.org’) should be passed through to the local SMTPlistener without modification. Be careful of mail loops if you do this!

Here’s 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 ssh;user esr is esr here

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 are suppressed. Apiece of mail is considered duplicate if it has the same message-ID 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.

Header vs. Envelope addresses

The fundamental problem is that by having your mailserver 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.

Sometimesfetchmail can deduce the envelope address. If the mailserver MTA issendmail and 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 doesn’t 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!

Whenfetchmail cannot 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’s 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 the themailserver 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’re fetching from (1) stores one copy of the message perrecipient in your domain and (2) records the envelopeinformation 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’ll 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 nameisn’t removed from alias expansions in messages you send.

This trick is not without its problems, however. You’ll 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 runningfetchmail, but the program has no way to know that that’s actually the right thing.

Bad Ways To Abuse Multidrop Mailboxes

Multidrop mailboxes andfetchmail serving 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. Unlessfetchmail can 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’re tempted to usefetchmail to 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 themailserver’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 mailserver’s expiry period). If you can’t arrangethis, try setting up a UUCP feed.

If you absolutely must use multidrop for this purpose, make sureyour mailserver 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 declaredfetchmail extracts recipient addresses as described above and checks each hostpart with DNS to see if it’s an alias of the mailserver. 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 mailserver aliases with ’aka’; these are checkedbefore DNS lookups are done. If you’re certain your aka list containsall DNS aliases of the mailserver (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.

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

The exit codes returned byfetchmail are as follows:

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

If the FETCHMAILUSER 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 userid gracefully).

If the environment variable FETCHMAILHOME is set to a valid andexisting directory name, fetchmail will read $FETCHMAILHOME/fetchmailrc(the dot is missing in this case), $FETCHMAILHOME/.fetchids and$FETCHMAILHOME/.fetchmail.pid rather than from the user’s homedirectory. The .netrc file is always looked for in the the invokinguser’s home directory regardless of FETCHMAILHOME’s setting.

If the HOME_ETC variable is set, fetchmail will read$HOME_ETC/.fetchmailrc instead of ~/.fetchmailrc.

If HOME_ETC and FETCHMAILHOME are set, HOME_ETC will be ignored.

If afetchmail daemon is running as root, SIGUSR1 wakes it up from its sleep phase andforces a poll of all non-skipped servers. For compatibility reasons,SIGHUP can also be used in 6.3.X but may not be available in futurefetchmail versions.

Iffetchmail is running in daemon mode as non-root, use SIGUSR1 to wake it (this isso SIGHUP due to logout can retain the default action of killing it).

Runningfetchmail in foreground while a background fetchmail is running will dowhichever of these is appropriate to wake it up.

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 6.3.X versions offetchmail won’t be fixed.

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

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 don’t get reaped until the endof the poll cycle. This can cause resource starvation if too manyzombies accumulate. So either don’t 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 mailserver.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 suid privileges it may have while running theMDA. For maximum safety, however, don’t 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 a~/.fetchmailrc while a background instance is running and break the syntax, thebackground instance will die silently. Unfortunately, it can’tdie noisily because we don’t yet know whether syslog should be enabled.On some systems, fetchmail dies quietly even if there is no syntaxerror; this seems to have something to do with buggy terminal ioctlcode in the kernel.

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

The ’principal’ option only handles Kerberos IV, not V.

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.

Send comments, bug reports, gripes, and the like to thefetchmail-devel list <fetchmail-devel@lists.berlios.de>. An HTML FAQ isavailable at the fetchmail home page; surf tohttp://fetchmail.berlios.de/ or do a WWW search for pages with’fetchmail’ in their titles.

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 from Eric S. Raymond <esr@snark.thyrsus.com>. Toomany other people to name here have contributed code and patches.

This program is descended from and replacespopclient, by Carl Harris <ceharris@mal.com>; the internals have become quite different,but some of its interface design is directly traceable to thatancestral program.

This manual page has been improved by R. Hannes Beinert and H[’e]ctorGarc[’i]a.

The fetchmail home page: <http://fetchmail.berlios.de/>

The maildrop home page: <http://www.courier-mta.org/maildrop/>

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