| Back to Fetchmail Home Page | $Date: 2004/01/13 08:46:00 $ |
Before reporting any bug, please read G3 for advice on how to include diagnostic information that will get your bug fixed as quickly as possible.
If you have a question or answer you think ought to be added to this FAQ list, mail it to fetchmail's maintainer, Eric S. Raymond, at esr@thyrsus.com.
Fetchmail is a one-stop solution to the remote mail retrieval problem for Unix machines, quite useful to anyone with an intermittent PPP or SLIP connection to a remote mailserver. It can collect mail using any variant of POP or IMAP and forwards via port 25 to the local SMTP listener, enabling all the normal forwarding/filtering/aliasing mechanisms that would apply to local mail or mail arriving via a full-time TCP/IP connection.
Fetchmail is not a toy or a coder's learning exercise, but an industrial-strength tool capable of transparently handling every retrieval demand from those of a simple single-user ISP connection up to mail retrieval and rerouting for an entire client domain. Fetchmail is easy to configure, unobtrusive in operation, powerful, feature-rich, and well documented.
Fetchmail is open-source software. The openness of the sources is the strongest assurance of quality you can have. Extensive peer review by a large, multi-platform user community has shown that fetchmail is as near bulletproof as the underlying protocols permit.
Fetchmail is licensed under the GNU General Public License.
If you found this FAQ in the distribution, see the README for fetchmail's full feature list.
The latest HTML FAQ is available alongside the latest fetchmail sources at the fetchmail home page: http://fetchmail.berlios.de/. You can also usually find both in the POP mail tools directory on Sunsite.
A text dump of this FAQ is included in the fetchmail distribution. Because it freezes at distribution release time, it may not be completely current.
Yes I will, provided you include enough diagnostic information for me to go on. Send bugs to fetchmail-friends. When reporting bugs, please include the following:
If you have FTP access to your remote mail account, and you have any suspicion that the bug was triggered by a particular message, please include a copy of the message that triggered the bug.
Often, the first thing I will do when you report a bug is tell you to upgrade to the newest version of fetchmail, and then see if the problem reproduces. So you'll probably save us both time if you upgrade and test with the latest version before sending in a bug report.
If your bug is something that used to work but stopped working when you upgraded, then you can help pin the bug down by trying intermediate versions of fetchmail until you identify the revision that broke your feature. The smart way to do this is by binary search on the version sequence. First, try the version halfway between your last good one and the current one. If it works, the failure was introduced in the upper half of the sequence; if it doesn't, the failure was introduced in the lower half. Now bisect that half in the same way. In a very few tries, you should be able to identify the exact adjacent pair of versions between which your bug was introduced -- and with information like that, I can usually come up with a fix very quickly.
Another useful thing you can do, if you're using POP3, is to test for IMAP4 support on your mailserver using the autoprobe function of fetchmailconf. If you have IMAP4, and fetchmailconf doesn't tell you it's broken, switch immediately. POP3 is a weak, poorly-designed protocol with chronic problems, and the later versions after RFC1725 actually get worse rather than better. Changing over to IMAP4 may well make your problem go away -- and if your ISP doesn't have IMAP4 support, bug them to supply it.
It is helpful if you include your .fetchmailrc file, but not necessary unless your symptom seems to involve an error in configuration parsing. If you do send in your .fetchmailrc, mask the passwords first!
If fetchmail seems to run and fetch mail, but the headers look mangled (that is, headers are missing or blank lines are inserted in the headers) then read the FAQ items in section X before submitting a bug report. Pay special attention to the item on diagnosing mail mangling. There are lots of ways for other programs in the mail chain to screw up that look like fetchmail's fault, but you may be able to fix these by tweaking your configuration.
A transcript of the failed session with -v -v (yes, that's two -v options, enabling debug mode) will almost always be useful. It is very important that the transcript include your POP/IMAP server's greeting line, so I can identify it in case of server problems. This transcript will not reveal your passwords, which are specially masked out precisely so transcripts can be passed around.
If you upgraded your fetchmail and something broke, you should include session transcripts with -v -v of both the working and failing versions. Very often, the source of the problem can instantly identified by looking at the differences in protocol transactions.
If the bug involves a core dump or hang, a gdb stack trace is good to have. (Bear in mind that you can attach gdb to a running but hung process by giving the process ID as a second argument.) You will need to reconfigure with:
CFLAGS=-g LDFLAGS=" " ./configure
Then rebuild in order to generate a version that can be gdb-traced.
Best of all is a mail file which, when fetched, will reproduce the bug under the latest (current) version.
Any bug I can reproduce will usually get fixed very quickly, often within 48 hours. Bugs I can't reproduce are a crapshoot. If the solution isn't obvious when I first look, it may evade me for a long time (or to put it another way, fetchmail is well enough tested that the easy bugs have long since been found). So if you want your bug fixed rapidly, it is not just sufficient but nearly necessary that you give me a way to reproduce it.
Probably not. Most of the feature suggestions I get are for ways to set various kinds of administrative policy or add more spam filtering (the most common one, which I used to get about four million times a week and got really tired of, is for tin-like kill files).
You can do spam filtering better with procmail or maildrop on
the server side and (if you're the server sysadmin) sendmail.cf
domain exclusions. If you really want fetchmail to do it from the
client side, yse a preconnect command to call
mailfilter.
You can do other policy things better with the
mda option and script wrappers around fetchmail. If
it's a prime-time-vs.-non-prime-time issue, ask yourself whether a
wrapper script called from crontab would do the job.
I'm not going to do these; fetchmail's job is transport, not policy, and I refuse to change it from doing one thing well to attempting many things badly. One of my objectives is to keep fetchmail simple so it stays reliable.
For reasons fetchmail doesn't have other commonly-requested features (such as password encryption, or multiple concurrent polls from the same instance of fetchmail) see ESR's design notes. Note that this document is partially obsoleted by the updated design notes.
Fetchmail is a mature project, no longer in constant active development. It is no longer my top project, and I am going to be quite reluctant to add features that might either jeopardize its stability or involve me in large amounts of coding.
All that said, if you have a feature idea that really is about a transport problem that can't be handled anywhere but fetchmail, lay it on me. I'm very accommodating about good ideas.
The second-most-requested feature for fetchmail, after
content-based filtering, is the ability to have it remove messages
from a maildrop after N days, typically to be used with the
keep option as a sort of poor man's newsgroup
facility. Microsoft's Outlook Express supports this.
This feature won't be added either. Repeat after me: fetchmail's job is transport, not policy. If you want this, write a Perl or Python script, to be run from a cron job, that deletes old messages off your maildrop. Send it to me and I'll put it in the contrib directory.
There is a fetchmail-friends list (fetchmail-friends@lists.ccil.org) for people who want to discuss fixes and improvements in fetchmail and help co-develop it. It's a MailMan list, which you can sign up for at http://lists.ccil.org/mailman/listinfo/fetchmail-friends. There is also an announcements-only list, fetchmail-announce@lists.ccil.org, which you can sign up for at http://lists.ccil.org/mailman/listinfo/fetchmail-announce.
The fetchmail development was also a sociological experiment, an extended test to see if my theory about the critical features of the Linux development model is correct.
The experiment was a success. I wrote a paper about it titled The Cathedral and the Bazaar which was first presented at Linux Kongress '97 in Bavaria and very well received there. It was also given at Atlanta Linux Expo, Linux Pro '97 in Warsaw, and the first Perl Conference, at UniForum '98, and was the basis of an invited presentation at Usenix '98. The folks at Netscape tell me it helped them decide to give away the source for Netscape Communicator.
If you're reading a non-HTML dump of this FAQ, you can find the paper on the Web with a search for that title.
The short answer: IMAP 2000 running over Unix.
Here's a longer answer:
Fetchmail will work with any POP, IMAP, ETRN, or ODMR server that conforms to the relevant RFCs (and even some outright broken ones like Microsoft Exchange and Novell GroupWise). This doesn't mean it works equally well with all, however. POP2 servers, and POP3 servers without LAST, limit fetchmail's capabilities in various ways described on the manual page.
Most modern Unixes (and effectively all Linux/*BSD systems) come with POP3 support preconfigured (but beware of the horribly broken POP3 server mentioned in D2). An increasing minority also feature IMAP (you can detect IMAP support by running fetchmail in AUTO mode, or by using the `Probe for supported protocols' function in the fetchmailconf utility).
If you have the option, we recommend using or installing an IMAP4rev1 server; it has the best facilities for tracking message `seen' states. It also recovers from interrupted connections more gracefully than POP3, and enables some significant performance optimizations. The new IMAP 2000 is particularly nice, as it supports CRAM-MD5 so you don't have to ship your mail password over the net en clair (fetchmail autodetects this capability). Older versions had support for GSSAPI giving a similar effect.
Don't be fooled by NT/Exchange propaganda. M$ Exchange is just plain broken (see item S2) and NT cannot handle the sustained load of a high-volume remote mail server. Even Microsoft itself knows better than to try this; their own Hotmail service runs over Solaris! For extended discussion, see John Kirch's excellent white paper on Unix vs. NT performance.
Source for a high-quality supported implementation of POP is available from the Eudora FTP site. Don't use 2.5, which has a rather restrictive license. The 2.5.2 version appears to restore the open-source license of previous versions.
Fetchmail will work with all popular mail transport programs. It also doesn't care which user agent you use, and user agents are as a rule almost equally indifferent to how mail is delivered into your system mailbox. So any of the popular Unix mail agents -- elm, pine, mh, or mutt -- will work fine with fetchmail.
All this having been said, I can't resist putting in a discreet plug for mutt. My own personal mail setup is sendmail plus fetchmail plus mutt. Mutt's interface is only a little different from that of its now-moribund ancestor elm, but its excellent handling of MIME and PGP put it in a class by itself. You won't need its built-in POP3 support, though; most of the mutt developers will cheerfully admit that fetchmail's is better :-).
Depending on what your mail server you are talking to, this ranges from trivial to impossible. It may even be next to useless.
Most people use fetchmail over phone wires (whether plain old copper or DSL), which are hard to tap. Anybody with the skill and resources to do this could get into your server mailbox with much less effort by subverting the server host. So if your provider setup is phone-company wire going straight into a service box, you probably don't need to worry.
In general there is little point in trying to secure your fetchmail transaction unless you trust the security of the server host you are retrieving mail from. Your vulnerability is more likely to be an insecure local network on the server end (e.g. to somebody with a TCP/IP packet sniffer intercepting Ethernet traffic between the modem concentrator or DSL POP you dial in to and the mailserver host).
Having realized this, you need to ask whether password encryption alone will really address your security exposure. If you think you might be snooped between server and client, it's better to use end-to-end encryption on your whole mail stream so none of it can be read. One of the advantages of fetchmail over conventional SMTP-push delivery is that you may be able to arrange this by using ssh(1); see K3.
Note that ssh is not a complete privacy solution either, as your mail could have been snooped in transit to your POP server from wherever it originated. For best security, agree with your correspondents to use a tool such as GPG (Gnu Privacy Guard) or PGP (Pretty Good Privacy).
If ssh/sshd isn't available, or you find it too complicated for you to set up, password encryption will at least keep a malicious cracker from deleting your mail, and require him to either tap your connection continuously or crack root on the server in order to read it.
You can deduce what encryptions your mail server has available
by looking at the server greeting line (and, for IMAP, the response
to a CAPABILITY query). Do a fetchmail -v to see
these, or telnet direct to the server port (110 for POP3, 143 for
IMAP).
If your mailserver is using IMAP 2000, you'll have CRAM-MD5 support built in. Fetchmail autodetects this; you can skip the rest of this section.
The POP3 facility you are most likely to have available is APOP.
This is a POP3 feature supported by many servers (fetchmailconf's
autoprobe facility will detect it and tell you if you have it). If
you see something in the greeting line that looks like an
angle-bracket-enclosed Internet address with a numeric left-hand
part, that's an APOP challenge (it will vary each time you log in).
You can register a secret on the host (using
popauth(8) or some program like it). Specify the
secret as your password in your .fetchmailrc; it will be used to
encrypt the current challenge, and the encrypted form will be sent
back the the server for verification.
Alternatively, you may have Kerberos available. This may require you to set up some magic files in your home directory on your client machine, but means you can omit specifying any password at all.
Fetchmail supports two different Kerberos schemes. One is a POP3 variant called KPOP; consult the documentation of your mail server to see if you have it (one clue is the string "krb-IV" in the greeting line on port 110). The other is an IMAP and POP3 facility described by RFC1731 and RFC1734. You can tell if this one is present by looking for AUTH=KERBEROS_V4 in the CAPABILITY response.
If you are fetching mail from a CompuServe POP3 account, you can use their RPA authentication (which works much like APOP). See I1 for details. If you are fetching mail from Microsoft Exchange using IMAP, you will be able to use NTLM.
Your POP3 server may have the RFC1938 OTP capability to use one-time passwords (if it doesn't, you can get OTP patches for the 2.2 version of the Qualcomm popper from Craig Metz). To check this, look for the string "otp-" in the greeting line. If you see it, and your fetchmail was built with OPIE support compiled in (see the distribution INSTALL file), fetchmail will detect it also. When using OTP, you will specify a password but it will not be sent en clair.
You can get both POP3 and IMAP OTP patches from Craig Metz at http://www.inner.net/pub/.
These patches use a SASL authentication method named "X-OTP" because there is not currently a standard way to do this; fetchmail also uses this method, so the two will interoperate happily. They better, because this is how Craig gets his mail ;-)
Finally, you can use SSL for complete end-to-end encryption if you have an SSL-enabled mailserver.
Yes. In order to avoid giving indigestion to certain picky MTAs (notably exim), fetchmail always makes the RCPT TO address it feeds the MTA a fully qualified one with a hostname part. Normally it does this by appending @ and "localhost", but when you are using Kerberos or ETRN mode it will append @ and your machine's fully-qualified domain name (FQDN).
Appending the FQDN can create problems when fetchmail is running in daemon mode and outlasts the dynamic IP address assignment your client machine had when it started up.
Since the new IP address (looked up at RCPT TO interpretation time) doesn't match the original, the most benign possible result is that your MTA thinks it's seeing a relaying attempt and refuses. More frequently, fetchmail will try to connect to a nonexistent host address and time out. Worst case, you could up forwarding your mail to the wrong machine!
Use the smtpaddress option to force the appended
hostname to one with a (fixed) IP address of 127.0.0.1 in your
/etc/hosts. (The name `localhost' will usually work;
or you can use the IP address itself).
Only one fetchmail option interacts directly with your IP
address, `interface'. This option can be used to set
the gateway device and restrict the IP address range fetchmail will
use. Such a restriction is sometimes useful for security reasons,
especially on multihomed sites. See C3.
I recommend against trying to set up the interface
option when initially developing your poll configuration -- it's
never necessary to do this just to get a link working. Get the link
working first, observe the actual address range you see on
connections, and add an interface option (if you need
one) later.
You can't use ETRN if you have a dynamic IP address (your ISP changes your IP address occasionally, possibly with every connect). You need to have your own registered domain and a definite IP address registered for that domain. The server needs to be configured to accept mail for your domain but then queue it to forward to your machine. ETRN just tells to server to flush its queue for your domain. Fetchmail doesn't actually get the mail in that case.
You can use On-Demand Mail Relay (ODMR) with a dynamic IP address; that's what it was designed for, and it provides capabilities very similar to ETRN. Unfortunately ODMR servers are not yet widely deployed, as of early 2001.
If you're using a dynamic-IP configuration, one other (non-fetchmail) problem you may run into with outgoing mail is that some sites will bounce your email because the hostname your giving them isn't real (and doesn't match what they get doing a reverse DNS on your dynamically-assigned IP address). If this happens, you need to hack your sendmail so it masquerades as your host. Setting
DMsmarthost.here
in your sendmail.cf will work, or you can set
MASQUERADE_AS(smarthost.here)
in the m4 configuration and do a reconfigure. (In both cases,
replace smarthost.here with the actual name of your
mailhost.) See the sendmail FAQ for
more details.
No. You can use fetchmail with SOCKS, the standard tool for indirecting TCP/IP through a firewall. You can find out about SOCKS, and download the SOCKS software including server and client code, at the SOCKS distribution site.
The specific recipe for using fetchmail with a firewall is at K1
A user asks: but how do we send mail out to the POP3 server? Do I need to implement another tool or will fetchmail do this too?
Fetchmail only handles the receiving side. The sendmail or other preinstalled MTA on your client machine will handle sending mail automatically; it will ship mail that is submitted while the connection is active, and put mail that is submitted while the connection is inactive into the outgoing queue.
Normally, sendmail is also run periodically (every 15 minutes on most Linux systems) in a mode that tries to ship all the mail in the outgoing queue. If you have set up something like pppd to automatically dial out when your kernel is called to open a TCP/IP connection, this will ensure that the mail gets out.
Fetchmail is fully Y2K-compliant.
Fetchmail could theoretically have problems when the 32-bit time_t counters roll over in 2038, but I doubt it. Timestamps aren't used for anything but log entry generation. Anyway, if you aren't running on a 64-bit machine by then, you'll deserve to lose.
No. Fetchmail is a mail transport agent, best understood as a protocol gateway between POP3/IMAP servers and SMTP. Disconnected operation requires an elaborate interactive client. It's a very different problem.
Fetchmail streams message bodies line-by-line; the most core it ever requires per message is enough memory to hold the RFC822 header, and that storage is freed when body processing begins. It is, accordingly, quite economical in its use of memory.
After startup time, a fetchmail running in daemon mode stats its configuration file once per poll cycle to see whether it has changed and should be rescanned. Other than that, a fetchmail in normal operation doesn't touch the disk at all; that job is left up to the MTA or MDA the fetchmail talks to.
Fetchmail's performance is usually bottlenecked by latency on the POP server or (less often) on the TCP/IP link to the server. This is not a problem readily solved by tuning fetchmail, or even by buying more TCP/IP capacity (which tends to improve bandwidth but not necessarily latency).
The vendor-supplied make on FreeBSD systems can only be used within FreeBSD's "scope", e.g. the ports collection. Type "gmake" to run GNU make and better things will happen.
In the immortal words of Alan Cox the last time this came up: ``Take the Solaris lex and stick it up the backside of a passing Sun salesman, then install flex and use that. All will be happier.''
I couldn't have put it better myself, and ain't going to try now.
(The same problem has been reported under HP-UX v10.20 and IRIX)
If you get errors resembling these
mxget.o(.text+0x35): undefined referenceto `__res_search' mxget.o(.text+0x99): undefined reference to`__dn_skipname' mxget.o(.text+0x11c): undefined reference to`__dn_expand' mxget.o(.text+0x187): undefined reference to`__dn_expand' make: *** [fetchmail] Error 1
then you must add "-lresolv" to the LOADLIBS line in your Makefile once you have installed the `bind' package.
If you get link errors involving dcgettext, like this:
rcfile_y.o: In function `yyparse': rcfile_y.o(.text+0x3aa): undefined reference to `dcgettext__' rcfile_y.o(.text+0x4f2): undefined reference to `dcgettext__' rcfile_y.o(.text+0x5ee): undefined reference to `dcgettext__' rcfile_y.o: In function `yyerror': rcfile_y.o(.text+0xc7c): undefined reference to `dcgettext__' rcfile_y.o(.text+0xcc8): undefined reference to `dcgettext__' rcfile_y.o(.text+0xdf9): more undefined references to `dcgettext__' follow
reconfigure with configure --with-included-gettext. This is due to some brain-damage in the GNU internationalization libraries.
Reconfigure with --disable-nls and recompile.
GNU gettext is an overengineered, fragile pile of crap. I have teetered on the brink of removing support for it entirely several times.
If you were using ETRN mode, change your smtphost option to a fetchdomains option.
The `via localhost' special case for use with ssh tunnelling is gone. Use the %h feature of plugin instead.
In 5.6.8, the preauth keyword and option were changed back to auth. The preauth synonym will still be supported through a few more point releases.
The imap-gss, imap-k4, and imap-login protocol types are gone. This is a result of a major re-factoring of the authentication machinery; fetchmail can now use Kerberos V4 and GSSAPI not just with IMAP but with POP3 servers that have RFC1734 support for the AUTH command.
When trying to identify you to an IMAP or POP mailserver, fetchmail now first tries methods that don't require a password (GSSAPI, KERBEROS_IV); then it looks for methods that mask your password (CRAM-MD5, X-OTP); and only if it the server doesn't support any of those will it ship your password en clair.
Setting the preauth option to any value other than `password' will prevent from looking for a password in your .netrc file or querying for it at startup time.
In 5.1.0, the auth keyword and option were changed to preauth.
If the dns option is on (the default), you may need
to make sure that any hostname you specify (for mail hosts or for
an SMTP target) is a canonical fully-qualified hostname). In order
to avoid DNS overhead and complications, fetchmail no longer tries
to derive the fetchmail client machine's canonical DNS name at
startup.
Just after the `via' option was introduced, I
realized that the interactions between the `via',
`aka', and `localdomains' options were
out of control. Their behavior had become complex and confusing, so
much so that I was no longer sure I understood it myself. Users
were being unpleasantly surprised.
Rather than add more options or crock the code, I re-thought it. The redesign simplified the code and made the options more orthogonal, but may have broken some complex multidrop configurations.
Any multidrop configurations that depended on the name just
after the `poll' or `skip' keyword being
still interpreted as a DNS name for address-matching purposes, even
in the presence of a `via' option, will break.
It is theoretically possible that other unusual configurations (such as those using a non-FQDN poll name to generate Kerberos IV tickets) might also break; the old behavior was sufficiently murky that we can't be sure. If you think this has happened to you, contact the maintainer.
The `remote' keyword has been changed to
`folder'. If you try to use the old keyword, the
parser will utter a warning.
It could be because you're using a .fetchmailrc that's written
in the old popclient syntax without an explicit
`username' keyword leading the first user entry
attached to a server entry.
This error can be triggered by having a user option such as
`keep' or `fetchall' before the first
explicit username. For example, if you write
poll openmail protocol pop3
keep user "Hal DeVore" there is hdevore here
the `keep' option will generate an entire user
entry with the default username (the name of fetchmail's invoking
user).
The popclient compatibility syntax was removed in 4.0. It complicated the configuration file grammar and confused users.
The `interface', `monitor' and
`batchlimit' options changed after 2.8.
They used to be global options with `set' syntax
like the batchlimit and logfile options. Now they're per-server
options, like `protocol'.
If you had something like
set interface = "sl0/10.0.2.15"
in your .fetchmailrc file, simply delete that line and insert `interface sl0/10.0.2.15' in the server options part of your `defaults' declaration.
Do similarly for any `monitor' or
`batchlimit' options.
Either upgrade to a post-5.0.5 fetchmail or put string quotes around it. :-)
The configuration file parser in older fetchmail versions treated any all-numeric token as a number, which confused it when it was expecting a name. String quoting forces the token's class.
The lexical analyzer in 5.0.6 and beyond is smarter and assumes any token following "username" or "password" is a string.
See F2. You're caught in an unfortunate crack between the newer-style syntax for negated options (`no keep', `no rewrite' etc.) and the older style run-on syntax (`nokeep', `norewrite' etc.).
Upgrade to a 5.0.6 or later fetchmail, or put string quotes around your token.
The most common cause of mysterious parse errors is putting a server option after a user option. Check the manual page; you'll probably find that by moving one or more options closer to the `poll' keyword you can eliminate the problem.
Yes, I know these ordering restrictions are hard to understand. Unfortunately, they're necessary in order to allow the `defaults' feature to work.
Ian T. Zimmerman <itz@rahul.net> asked:
On the machine where I'm the only real user, I run fetchmail as root from a cron job, like this:
fetchmail -u "itz" -p POP3 -s bolero.rahul.net
This used to work as is (with no .fetchmailrc file in root's home directory) with the last version I had (1.7 or 1.8, I don't remember). But with 2.0, it RECPs all mail to the local root user, unless I create a .fetchmailrc in root's home directory containing:
skip bolero.rahul.net proto POP3
user itz is itz
It won't work if the second line is just "user
itz". This is silly.
It seems fetchmail decides to RECP the `default local user' (i.e. the uid running fetchmail) unless there are local aliases, and the `default' aliases (itz->itz) don't count. They should.
Answer:
No they shouldn't. I thought about this for a while, and I don't much like the conclusion I reached, but it's unavoidable. The problem is that fetchmail has no way to know, in general, that a local user `itz' actually exists.
"Ah!" you say, "Why doesn't it check the password file to see if the remote name matches a local one?" Well, there are two reasons.
One: it's not always possible. Suppose you have an SMTP host declared that's not the machine fetchmail is running on? You lose.
Two: How do you know server itz and SMTP-host itz are the same person? They might not be, and fetchmail shouldn't assume they are unless local-itz can explicitly produce credentials to prove it (that is, the server-itz password in local-itz's .fetchmailrc file.).
Once you start running down possible failure modes and thinking about ways to tinker with the mapping rules, you'll quickly find that all the alternatives to the present default are worse or unacceptably more complicated or both.
The easiest way to dispatch fetchmail on logout (which will work reliably only if you have just one login going at any time) is to arrange for the command `fetchmail -q' to be called on logout. Under bash, you can arrange this by putting `fetchmail -q' in the file `~/.bash_logout'. Most csh variants execute `~/.logout' on logout. For other shells, consult your shell manual page.
Automatic startup/shutdown of fetchmail is a little harder to arrange if you may have multiple login sessions going. In the contrib subdirectory of the fetchmail distribution there is some shell code you can add to your .bash_login and .bash_logout profiles that will accomplish this. Thank James Laferriere <babydr@nwrain.net> for it.
Some people start up and shut down fetchmail using the ppp-up and ppp-down scripts of pppd.
This depends a lot on your local networking configuration (and right now you can't use it at all except under Linux and the newer BSDs). However, here are some important rules of thumb that can help. If they don't work, ask your local sysop or your Internet provider.
First, you may not need to use --interface at all. If your machine only ever does SLIP or PPP to one provider, it's almost certainly by a point to point modem connection to your provider's local subnet that's pretty secure against snooping (unless someone can tap your phone or the provider's local subnet!). Under these circumstances, specifying an interface address is fairly pointless.
What the option is really for is sites that use more than one provider. Under these circumstances, typically one of your provider IP addresses is your mailserver (reachable fairly securely via the modem and provider's subnet) but the others might ship your packets (including your password) over unknown portions of the general Internet that could be vulnerable to snooping. What you'll use --interface for is to make sure your password only goes over the one secure link.
To determine the device:
To determine the address and netmask:
To illustrate the rule for dynamic IP addresses, let's suppose you're hooked up via SLIP and your IP provider tells you that the dynamic address pool is 255 addresses ranging from 205.164.136.1 to 205.164.136.255. Then
interface "sl0/205.164.136.0/255.255.255.0"
would work. To range over any value of the last two octets (65536 addresses) you would use
interface "sl0/205.164.0.0/255.255.0.0"
This answer covers versions of sendmail from 8.9.3-20 (the version installed in Red Hat 6.2) upwards. If you have an older version, upgrade to sendmail 8.9.
Stock sendmails can now do anti-spam exclusions based on a database of filter rules. The human-readable form of the database is at /etc/mail/access. The database itself is at /etc/mail/access.db.
The table itself uses email addresses, domain names, and network numbers as keys. For example,
spammer@aol.com REJECT cyberspammer.com REJECT 192.168.212 REJECT
would refuse mail from spammer@aol.com, any user from cyberspammer.com (or any host within the cyberspammer.com domain), and any host on the 192.168.212.* network. (This feature can be used to do other things as well; see the sendmail documentation for details)
To actually set up the database, run
makemap hash deny <deny
in /etc/mail.
To test, send a message to your mailing address from that host and then pop off the message with fetchmail, using the -v argument. You can monitor the SMTP transaction, and when the FROM address is parsed, if sendmail sees that it is an address in spamlist, fetchmail will flush and delete it.
Under no circumstances put your mailhost or any host you accept mail from using fetchmail into your reject file. You will lose mail if you do this!!!
Use the interval keyword on the ones that should be checked less often. For example, if you do a poll every 5 minutes, and want to poll some mailboxes every 5 minutes and some every 30 minutes, use something like this:
poll mainsite.example.com proto pop3 user .... poll secondary.example.com proto pop3 interval 6 user ...
Then secondary.example.com will be polled every 6th time that mainsite.example.com is polled, which with a polling interval of every 5 minutes means that secondary.example.com will be polled every 30 minutes.
Often, startup scripts have a different environment than an interactive login shell. For instance, $HOME might point to "/root" when you are logged in as root, but it might be either unset, or set to "/" when the startup scripts are running. That means fetchmail at startup can't find the .fetchmailrc.
Pick a location (such as /etc/fetchmailrc) and use fetchmail's -f option to point fetchmail at it. That should solve the problem.
To forward mail to a host other than the one you are running
fetchmail on, use the smtphost or
smtpname option. See the manual page for details.
For most sendmails, no special configuration is required. Eric
Allman tells me that if FEATURE(always_add_domain) is
included in sendmail's configuration, you can leave the
rewrite option off.
If your sendmail complains ``sendmail does not relay'', make
sure your sendmail.cf file says Cwlocalhost so that
sendmail recognizes `localhost' as a name of its host.
If you're mailing from another machine on your local network, also ensure that its IP address is listed in ip_allow or name in name_allow (usually in /etc/mail/)
If you find that your sendmail doesn't like the address
`FETCHMAIL-DAEMON@localhost' (which is used in the bouncemail that
fetchmail generates), you may have to set
FEATURE(accept_unqualified_senders).
Günther Leber reports that Digital Unix sendmails won't
work with fetchmail. The symptom is an error message "553
Local configuration error, hostname not recognized as
local". The problem is that fetchmail normally feeds
sendmail with the client machine's host address in the MAIL FROM
line. These sendmails think this means they're seeing the result of
a mail loop and suppress the mail. You may be able to work around
this by running in --invisible mode.
If you want to support multidrop mode, and you can get access to your mailserver's sendmail.cf file, it's a good idea to add this rule:
H?l?Delivered-To: $h
This will cause the mailserver's sendmail to reliably write the appropriate envelope address into each message before fetchmail sees it, and tell fetchmail which header it is. With this change, multidrop mode should work reliably even when the Received header omits the envelope address (which will typically be the case when the message has multiple recipients). However it will still not distinguish the recipients, your only advantage is that no bounce will be sent if a message is BCC addressed to multiple users at your site. To fix even that problem, you might want to try the following hack, which is however untested and quite experimental:
H?J?Delivered-To: $u
Mmdrop, P=/usr/bin/procmail, F=lsDFMqSPfhnu9J,
S=EnvFromSMTP/HdrFromSMTP, R=EnvToSMTP/HdrToSMTP,
T=DNS/RFC822/X-Unix,
A=procmail -Y -a $u -d $h
For both hacks, you have to declare `envelope
"Delivered-To:"' on the fetchmail side, to put the virtual
domain (e.g. `domain.com') with RELAY permission into your access
file and to add a line reading `domain.com
local:local-pop-user' for the first and `domain.com
mdrop:local-pop-user' for the second hack to your
mailertable.
You will notice that if the mail already has a Delivered-To header, sendmail will not add another. Further, editing sendmail.cf directly is not very comfortable. Solutions for both problems can be found in Peter `Rattacresh' Backes' `hybrid' patch against sendmail. Have a look at it, you can find it in the contrib subdirectory.
Feel free to try Martijn Lievaart's detailed recipe in the contrib subdirectory of the fetchmail source distribution, it attempts to realize multidrop mailboxes with an external script.
If for some reason you are invoking sendmail via the mda option (rather than delivering to port 25 via smtp), don't forget to include the -i switch. Otherwise you will occasionally get mysterious delivery failures with a SIGPIPE as the sendmail instance dies. The problem is messages with a single dot at start of a text line.
Turn on the forcecr option; qmail's listener mode
doesn't like header or message lines terminated with bare
linefeeds.
(This information is thanks to Robert de Bath <robert@mayday.cix.co.uk>.)
If a mailhost is using the qmail package (see http://pobox.com/~djb/qmail.html) then, providing the local hosts are also using qmail, it is possible to set up one fetchmail link to be reliably collect the mail for an entire domain.
One of the basic features of qmail is the `Delivered-To:' message header. Whenever qmail delivers a message to a local mailbox it puts the username and hostname of the envelope recipient on this line. The major reason for this is to prevent mail loops.
To set up qmail to batch mail for a disconnected site the ISP-mailhost will have normally put that site in its `virtualhosts' control file so it will add a prefix to all mail addresses for this site. This results in mail sent to 'username@userhost.userdom.dom.com' having a 'Delivered-To:' line of the form:
Delivered-To: mbox-userstr-username@userhost.userdom.dom.com
A single host maildrop will be slightly simpler:
Delivered-To: mbox-userstr-username@userhost.dom.com
The ISP can make the 'mbox-userstr-' prefix anything they choose but a string matching the user host name is likely.
To use this line you must:
So far this reliably delivers messages to the correct machine of the local network, to deliver to the correct user the 'mbox-userstr-' prefix must be stripped off of the user name. This can be done by setting up an alias within the qmail MTA on each local machine. Simply create a dot-qmail file called '.qmail-mbox-userstr-default' in the alias directory (normally /var/qmail/alias) with the contents:
| ../bin/qmail-inject -a -f"$SENDER" "${LOCAL#mbox-userstr-}@$HOST"
Note this does require a modern /bin/sh.
Peter Wilson adds:
``My ISP uses "alias-unzzippedcom-" as the prefix, which means that I need to name my file ".qmail-unzzippedcom-default". This is due to qmail's assumption that a message sent to user-xyz is handled by the file ~user/.qmail-xyz (or ~user/.qmail-default).''
Luca Olivetti adds:
If you aren't using qmail locally, or you don't want to set up
the alias mechanism described above, you can use the option
`qvirtual "mbox-userstr-"' in your fetchmail config
file to strip the prefix from the local user name.
If you have rewrite on:
There is an RFC1123 requirement that MAIL FROM and RCPT TO addresses you pass to it have to be canonical (e.g. with a fully qualified hostname part). Therefore fetchmail tries to pass fully qualified RCPT TO addresses. But exim does not by default accept `localhost' as a fully qualified domain. This can be fixed.
In exim.conf, add `localhost' to your local_domains declaration if it's not already present. For example, the author's site at thyrsus.com would have a line reading:
local_domains = thyrsus.com:localhost
If you have rewrite off:
MAIL FROM is a potential problem if the MTAs upstream from your
fetchmail don't necessarily pass canonicalized From and Return-Path
addresses, and fetchmail's rewrite option is off. The
specific case where this has come up involves bounce messages
generated by sendmail on your mailer host, which have the
(un-canonicalized) origin address MAILER-DAEMON.
The right way to fix this is to enable the rewrite
option and have fetchmail canonicalize From and Return-Path
addresses with the mailserver hostname before exim sees them. This
option is enabled by default, so it won't be off unless you turned
it off.
If you must run with rewrite off, there is a switch
in exim's configuration files that allows it to accept domainless
MAIL FROM addresses; you will have to flip it by putting the
line
sender_unqualified_hosts = localhost
in the main section of the exim configuration file. Note that this will result in such messages having an incorrect domain name attached to their return address (your SMTP listener's hostname rather than that of the remote mail server).
Smail 3.2 is very nearly plug-compatible with sendmail, and may work fine out of the box.
We have one report that when processing multiple messages from a single fetchmail session, smail sometimes delivers them in an order other than received-date order. This can be annoying because it scrambles conversational threads. This is not fetchmail's problem, it is an smail `feature' and has been reported to the maintainers as a bug.
Very recent smail versions require an
-smtp_hello_verify option in the smail config file.
This overrides smail's check to see that the HELO address is
actually that of the client machine, which is never going to be the
case when fetchmail is in the picture. According to RFC1123 an SMTP
listener must allow this mismatch, so smail's new behavior
(introduced sometime between 3.2.0.90 and 3.2.0.95) is a bug.
You may also need to say
-smtp_hello_broken_allow=127.0.0.1 in order for smail
to accept the "localhost" that fetchmail normally appends to
recipient addresses.
MMDF itself is difficult to configure, but it turns out that connecting fetchmail to MMDF's SMTP channel isn't that hard. You can read an MMDF recipe that describes replacing a UUCP link with fetchmail feeding MMDF.
The Lotus Notes SMTP gateway tries to deduce when it should convert \n to \r\n, but its rules are not the intuitive and correct-for-RFC822 ones. Use `forcecr'.
The courier mta doesn't like RCPT addresses that look like
someone@localhost. Work around this with an
smtphost or smtpaddress.
vbmailshield's SMTP interpreter is broken. It doesn't understand RSET.
As a workaround, you can set batchlimit to 1 so RSET is never used.
Qualcomm's qpopper is probably the best-of-breed among POP3 servers, and is very widely deployed. Nevertheless, it has some problems which fetchmail exposes. We recommend using IMAP instead if at all possible. If you must talk to qpopper, here are some problems to be aware of:
Tony Tang <tony@atn.com.hk> reports that there is a bad intercation between fetchmail and qpopper 2.5.3 under Red Hat Linux versions 5.0 to 5.2, kernels 2.0.34 to 2.0.35. When fetching very large messages (over 700K) from 2.5.3, fetchmail will hang with a socket error.
This is probably not a fetchmail bug, but rather a symptom of some problem in the networking stack that qpopper's transmission pattern is tickling, as fetchpop (another Linux POP client) also displays the hang but Netscape running under Win95 does not. The problem can also be banished by upgrading to qpopper 3.0b1.
Versions of fetchmail from 4.4.2 through 4.4.7 had a bad interaction with Eudora qpopper versions 2.3 and later. See X5 for details. The solution is to upgrade your fetchmail.
It's been reliably reported that Exchange 2000's POP3 support is so broken that it's unusable. One symptom is that messages without a terminating newline get the POP3 message termination dot emitted -- you guessed it -- right after the last character of the message, with no terminating newline added. This will hang fetchmail or any other RFC-compliant server. IMAP is alleged to work OK, though.
Older versions of Exchange are semi-usable. They randomly drop attachments on the floor, though. Microsoft acknowledges this as a known bug and apparently has no plans to fix it.
Fetchmail using IMAP supports the proprietary NTLM mode used with M$ Exchange servers. To enable this, configure fetchmail with the --enable-NTLM option and recompile it. Specify a user option value that looks like `user@domain': the part to the left of the @ will be passed as the username and the part to the right as the NTLM domain.
M$ Exchan
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<hr><h1>Static String Functions.</h1>Replacements for the standard C string functions.
<a href="#_details">More...</a><table border=0 cellpadding=0 cellspacing=0>
<tr><td colspan=2><br><h2>Functions</h2></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a0">trio_create</a> (size_t size)</td></tr>
<tr><td> </td><td><font size=-1><em>Create new string.</em> <a href="#a0">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC void </td><td valign=bottom><a class="el" href="group___static_strings.html#a1">trio_destroy</a> (char *string)</td></tr>
<tr><td> </td><td><font size=-1><em>Destroy string.</em> <a href="#a1">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC size_t </td><td valign=bottom><a class="el" href="group___static_strings.html#a2">trio_length</a> (const char *string)</td></tr>
<tr><td> </td><td><font size=-1><em>Count the number of characters in a string.</em> <a href="#a2">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a3">trio_append</a> (char *target, const char *source)</td></tr>
<tr><td> </td><td><font size=-1><em>Append <code>source</code> at the end of <code>target</code>.</em> <a href="#a3">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a4">trio_append_max</a> (char *target, size_t max, const char *source)</td></tr>
<tr><td> </td><td><font size=-1><em>Append at most <code>max</code> characters from <code>source</code> to <code>target</code>.</em> <a href="#a4">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a5">trio_contains</a> (const char *string, const char *substring)</td></tr>
<tr><td> </td><td><font size=-1><em>Determine if a string contains a substring.</em> <a href="#a5">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a6">trio_copy</a> (char *target, const char *source)</td></tr>
<tr><td> </td><td><font size=-1><em>Copy <code>source</code> to <code>target</code>.</em> <a href="#a6">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a7">trio_copy_max</a> (char *target, size_t max, const char *source)</td></tr>
<tr><td> </td><td><font size=-1><em>Copy at most <code>max</code> characters from <code>source</code> to <code>target</code>.</em> <a href="#a7">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a9">trio_duplicate</a> (const char *source)</td></tr>
<tr><td> </td><td><font size=-1><em>Duplicate <code>source</code>.</em> <a href="#a9">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a10">trio_duplicate_max</a> (const char *source, size_t max)</td></tr>
<tr><td> </td><td><font size=-1><em>Duplicate at most <code>max</code> characters of <code>source</code>.</em> <a href="#a10">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a11">trio_equal</a> (const char *first, const char *second)</td></tr>
<tr><td> </td><td><font size=-1><em>Compare if two strings are equal.</em> <a href="#a11">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a12">trio_equal_case</a> (const char *first, const char *second)</td></tr>
<tr><td> </td><td><font size=-1><em>Compare if two strings are equal.</em> <a href="#a12">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a13">trio_equal_case_max</a> (const char *first, size_t max, const char *second)</td></tr>
<tr><td> </td><td><font size=-1><em>Compare if two strings up until the first <code>max</code> characters are equal.</em> <a href="#a13">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a14">trio_equal_locale</a> (const char *first, const char *second)</td></tr>
<tr><td> </td><td><font size=-1><em>Compare if two strings are equal.</em> <a href="#a14">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a15">trio_equal_max</a> (const char *first, size_t max, const char *second)</td></tr>
<tr><td> </td><td><font size=-1><em>Compare if two strings up until the first <code>max</code> characters are equal.</em> <a href="#a15">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC const char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a16">trio_error</a> (int error_number)</td></tr>
<tr><td> </td><td><font size=-1><em>Provide a textual description of an error code (errno).</em> <a href="#a16">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC size_t </td><td valign=bottom><a class="el" href="group___static_strings.html#a17">trio_format_date_max</a> (char *target, size_t max, const char *format, const struct tm *datetime)</td></tr>
<tr><td> </td><td><font size=-1><em>Format the date/time according to <code>format</code>.</em> <a href="#a17">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC unsigned <br>
long </td><td valign=bottom><a class="el" href="group___static_strings.html#a18">trio_hash</a> (const char *string, int type)</td></tr>
<tr><td> </td><td><font size=-1><em>Calculate a hash value for a string.</em> <a href="#a18">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a19">trio_index</a> (const char *string, int character)</td></tr>
<tr><td> </td><td><font size=-1><em>Find first occurrence of a character in a string.</em> <a href="#a19">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a20">trio_index_last</a> (const char *string, int character)</td></tr>
<tr><td> </td><td><font size=-1><em>Find last occurrence of a character in a string.</em> <a href="#a20">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a21">trio_lower</a> (char *target)</td></tr>
<tr><td> </td><td><font size=-1><em>Convert the alphabetic letters in the string to lower-case.</em> <a href="#a21">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a22">trio_match</a> (const char *string, const char *pattern)</td></tr>
<tr><td> </td><td><font size=-1><em>Compare two strings using wildcards.</em> <a href="#a22">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC int </td><td valign=bottom><a class="el" href="group___static_strings.html#a23">trio_match_case</a> (const char *string, const char *pattern)</td></tr>
<tr><td> </td><td><font size=-1><em>Compare two strings using wildcards.</em> <a href="#a23">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC size_t </td><td valign=bottom><a class="el" href="group___static_strings.html#a24">trio_span_function</a> (char *target, const char *source, int(*Function)(int))</td></tr>
<tr><td> </td><td><font size=-1><em>Execute a function on each character in string.</em> <a href="#a24">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a25">trio_substring</a> (const char *string, const char *substring)</td></tr>
<tr><td> </td><td><font size=-1><em>Search for a substring in a string.</em> <a href="#a25">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char * </td><td valign=bottom><a class="el" href="group___static_strings.html#a26">trio_substring_max</a> (const char *string, size_t max, const char *substring)</td></tr>
<tr><td> </td><td><font size=-1><em>Search for a substring in the first <code>max</code> characters of a string.</em> <a href="#a26">More...</a><em></em></font><br><br></td></tr>
<tr><td nowrap align=right valign=top>TRIO_STRING_PUBLIC char *