Cyrus IMAP Server FAQ

      * POP-Before-SMTP It is not included in the default distribution
        because there is already a standard way of doing this with SMTP
        AUTH. Any good MTA and/or MUA should support SMTP AUTH, so we
        shouldn't have to create a hack in an unrelated service. However,
        if you would like to install it anyway, we recommend using DRAC,
        along with the patch available in contrib/drac_auth.patch. 
      * Using NFS We don't recommend it. If you want to do it, it may
        possibly work but you may also lose your email or have corrupted
        cyrus.* files. You can look at the mailing list archives for more
        information. 
      * Using AFS/Coda We don't recommend it. It's even less likely to work
        than NFS. If you want to do it, it may possibly work but you may
        also lose your email or have corrupted cyrus.* files. CMU's
        previous e-mail system, AMS, leveraged AFS extensively for storage
        (and transit) purposes. For various reasons it didn't scale
        particularly well and led to CMU's interest in IMAP. 

        Cyrus was designed to use a local filesystem with Unix semantics
        and a working mmap()/write() combination. AFS doesn't provide these
        semantics so won't work correctly. 
      * Virtual hosting - See virtual domains configuration. 
      * dots in userids - you can have a '.' in your username IF, AND ONLY
        IF, you use the UNIX hierarchy convention. 
      * renaming users - Supported, but try to make sure that the user is
        not, and can not login when doing the rename. Otherwise user-meta
        may get corrupted and/or out of sync. 
      * plus addressing - Plus addressing allows direct delivery to a
        particular mailbox (other than an INBOX). This is done in two ways. 

        The first way allows delivery to a subfolder of a specific user's
        INBOX. This is done via an address of the form:
        username+mailfolder@domain, which will deliver to the user's
        INBOX.mailfolder folder (or altnamespace equivalent). This
        submailbox must allow the posting user the 'p' right (generally,
        this means 'anyone' must have the 'p' right), otherwise the message
        will just be filed into the user's INBOX. 

        The second way is to form an address like
        [postuser]+mailfolder@domain. This will deliver into the mailbox
        'mailfolder'. [postuser] is the string specified in the imapd.conf
        option of the same name, and may be the empty string. As before,
        the posting user will need to have the 'p' right on the mailbox. 

        For both methods, if 'mailfolder' is more than one level deep, you
        will need to conform to the hierarchy separator appropriate to your
        site. 
      * Performance/Capacity/Scaling - See the performance guide. 

General Questions

    Q: What are the advantages of LMTP? 
            

            A: LMTP protocol differs from SMTP in that it causes the Cyrus
            to return, after the final "." of the DATA command, one reply
            for each recipient. If, for example, a server is given a
            transaction for two recipients, delivery to the first succeeds,
            and delivery to the second encounters a temporary failure
            condition, the MTA will get a separate response for each
            recipient and will only have to reattempt to deliver it to the
            second recipient. If using SMTP, only a single temporary
            failure response would be returned, and the entire transaction
            would have to be reattempted. 

            Furthermore, LMTP is superior to invoking command-line delivery
            agents from the MTA in that most ESMTP extensions are supported
            by LMTP, without having to extend any interfaces. 

            Lastly, because LMTP can be run over TCP, it allows you to run
            SMTP (and spam/virus scanning) and mailbox access on separate
            servers, thus allowing better scalability. 
    Q: How do I configure my MTA? 
            

            A: See Configuring the Mail Transfer Agent 
    Q: How should I configure partitions to deal with a large number of
            users? 
            

            A: The key is not to over-subscribe any partitions. Avoid
            putting too many users on any one partition, such that
            read/write performance becomes unacceptable. Good RAID
            performance (plenty of read/write cache, and perhaps RAID 10
            instead of RAID 5) will improve the number of users a partition
            can serve. To benefit from multiple partitions, each should be
            on its own set of disks, served by an unsaturated interface
            (FC, SCSI, SAS, SATA, etc) to the host running Cyrus. 

            See the performance guide or general performance guidelines.
            Also see metapartition_files and metapartition-name in
            imapd.conf.5 for additional configuration options which can
            help with performance, especially if you have access to
            high-speed storage (faster than disks). 

Troubleshooting

    Q: Why doesn't imapd/pop3d/nntpd/lmtpd/timsieved advertise PLAIN or
            plaintext login commands? 
            

            A: Unless otherwise configured, Cyrus services only advertise
            PLAIN or plaintext login commands on encrypted connections
            (SSL-wrapped connections or after a successful STARTTLS
            command). This behavior can be changed with the use of the
            allowplaintext option in imapd.conf.5. 
    Q: I'm getting syslog'd messages from the master process saying
            processes are "signaled to death by 10". What's up? 
            

            A: If you're using Berkeley DB 3.0.55, try installing some
            patches to Berkeley DB available from
            http://www.sleepycat.com/update/3.0.55/patch.3.0.55.html. 
    Q: I've used saslpasswd2 to create CRAM-MD5 secrets, but imapd doesn't
            say AUTH=CRAM-MD5. Why? 
            

            A: Make sure /etc/sasldb2 is readable by the Cyrus user. 
    Q: I'm using "sasl_pwcheck_method: saslauthd", but authentication isn't
            working. 
            

            A: Make sure that the saslauthd daemon is running (you'll want
            to start it when the system boots). imapd is unable to connect
            to saslauthd if the following message appears in the logs: 

            Dec  6 12:58:57 mail3.andrew.cmu.edu imapd[1297]: cannot connect to saslauthd server

            Make sure that saslauthd is running and that the cyrus user can
            access the unix domain socket (defaults to /var/run/mux). 
    Q: I'm getting messages about "duplicate_prune". What's wrong? 
            

            A: These messages look like 

            Jan 14 13:46:24 grant ctl_deliver[9060]: duplicate_prune: opening
              /var/imap/deliverdb/deliver-x.db: No such file or directory
            Jan 14 13:46:24 grant ctl_deliver[9060]: duplicate_prune: opening
              /var/imap/deliverdb/deliver-y.db: No such file or directory
            Jan 14 13:46:24 grant ctl_deliver[9060]: duplicate_prune: opening
              /var/imap/deliverdb/deliver-z.db: No such file or directory

            These messages are normal; one file is maintained for each user
            beginning with "x", "y", "z", etc. If you're first starting or
            you have no users beginning with these letters, these messages
            are completely normal and can be ignored. 
    Q: I'm getting a message about "imapd: could not getenv(CYRUS_SERVICE);
            exiting" in my imapd.log. What's wrong? 
            

            A: Remove all imap, pop, lmtp and sieve lines from
            [x]inetd.conf and restart [x]inetd. Cyrus is run out of its own
            "master" process. 
    Q: How do I use different SSL/TLS certificates for imap and pop? 
            

            A: Specify the different certs using the appropriate options in
            imapd.conf. Read imapd.conf(5) for details. 
    Q: My KPOP client is complaining about TLS keys. What should I do? 
            

            A: Disable TLS for the kpop service. Either set
            tls_pop3_cert_file to disabled in imapd.conf (which will also
            disable SSL/TLS for pop3), or use a separate config file for
            kpop. For example, change the kpop service in cyrus.conf to
            something like: 

            kpop    cmd="pop3d -k -C /etc/kpopd.conf" listen="kpop"

            then copy /etc/imapd.conf to /etc/kpopd.conf and remove the
            tls_* options. 
    Q: Eudora 5.x can't connect using STARTTLS ("SSL Neogotiation Failed").
            What should I do? 
            

            A: First, complain to QUALCOMM because their STARTTLS
            implementation is broken. Eudora doesn't support TLSv1 (per
            RFC2246) and Cyrus requires it. If you really need this before
            it is fixed in Eudora, remove or comment out the following
            lines in tls.c: 

                if (tlsonly) {
                    off |= SSL_OP_NO_SSLv2;
                    off |= SSL_OP_NO_SSLv3;
                }

    Q: I'm getting messages in imapd.log like: 

            Sep 11 17:23:55 ogg lmtpd[773]: DBERROR db3: 16 lockers
            Sep 11 17:23:55 ogg lmtpd[1409]: DBERROR db3: 17 lockers
            Sep 11 17:23:56 ogg lmtpd[1508]: DBERROR db3: 9 lockers
            Sep 11 17:23:56 ogg lmtpd[776]: DBERROR db3: 9 lockers

            What's wrong? 
            

            A: Nothing is wrong. These messages are logged whenever
            Berkeley DB encounters lock contention, but aren't necessarily
            problems. This is especially likely when you have an empty or
            small duplicate delivery database and are receiving a large
            volume of e-mail. 

            Berkeley DB 4.0 has a bug where the number of lockers isn't
            decremented properly, causing this number to be unreliable. 
    Q: All of the 8bit characters in the headers of messages that I receive
            are being changed to 'X's. What's going on? 
            

            A: 8-bit characters are illegal in message headers. Following
            the principle of "be liberal in what you accept, and strict in
            what you send", Cyrus converts them to Xs. (Without a character
            set, having the 8-bit characters replaced with Xs is just as
            good as having them be any other 8-bit character, especially
            for sorting and searching). Alternatively, you can set
            "reject8bit: t" in imapd.conf to reject the messages outright.
            It might also be reasonable for Cyrus to support the use of a
            default character set, however thus far no one has done the
            work to do so (it would also involve QP-encoding the corrupted
            headers). 
    Q: Why can't I delete any messages from my over-quota mailbox? I'm
            using a client with a 'trash folder'. 
            

            A: Trash folders, as they are commonly implemented (as actual
            IMAP mailboxes), do not fit the IMAP delete/expunge model very
            well. In fact, naive client implementations will get stuck in a
            situation where they cannot delete a message from a mailbox
            because they try to COPY it to the trash folder before deleting
            the message. This operation will fail due to the mailbox being
            over quota. This is separate from the fact that a specific
            mailbox name is not interoperable between clients (one might
            call it 'trash', another 'Trash', another 'Recycle Bin', etc) 

            Given the lack of protocol support for a trash folder, this is
            mostly a quality-of-implementation issue on the client side.
            There are a few options here: 

              * Contact your client vendor to have the broken client fixed
                (one possibility is to have the client ask the user if they
                wish to permanantly delete the message if the COPY
                operation fails). 
              * Stop using the 'trash mailbox' feature of your client (if
                possible). 
              * Set a separate quota root on the 'trash folders' of users.
                This last option is significantly harder to do correctly,
                since it assumes that all clients that make use of a trash
                folder do so with the same folder name. 

    Q: How do I stop Cyrus from advertising the DIGEST-MD5 and CRAM-MD5
            shared secret SASL mechanisms? 
            

            A: Not really a Cyrus IMAPd question, this can be fixed by just
            removing the SASL plugins from where Cyrus SASL installed them
            (if no other applications require them), or by using the
            sasl_mech_list imapd.conf option to list only the mechanisms
            that you require. 

