Mailbox Formats
===============

Mailbox formats supported by Dovecot:

 * <mbox> [MailboxFormat.mbox.txt]: Traditional UNIX mailbox format. Users'
   INBOX mboxes are commonly stored in '/var/spool/mail' or '/var/mail'
   directory. Single file contains multiple messages.
 * <Maildir> [MailboxFormat.Maildir.txt]: One file contains one message. A
   reliable choice since files are never modified and all operations are
   atomic. The top-level 'Maildir' directory contains the 'Maildir/cur',
   'Maildir/new' and 'Maildir/tmp' subdirectories.
 * <dbox> [MailboxFormat.dbox.txt]: Dovecot's own high performance mailbox
   format. Mails are stored in one or more files, each containing one or more
   messages.
 * <Cydir> [MailboxFormat.Cydir.txt]: Dovecot's own simple and high performance
   Cyrus-like mailbox format. It should be mostly used for testing and
   benchmarking only. v1.1+ only.

Mailbox formats *not* supported by Dovecot:

 * <mbx> [MailboxFormat.mbx.txt]: UW-IMAP's old high performance mailbox
   format. One file contains all the mailboxes, so expunges may still be slow.
 * <mix> [MailboxFormat.mix.txt]: UW-IMAP's new (2006) high performance mailbox
   format. Similar to dbox.
 * <mailstore> [MailboxFormat.mailstore.txt]: A format created by Exim.
 * <MH> [MailboxFormat.MH.txt]: One file contains one message. Sort order of
   the folder determines the message ID and name.  Actively used by projects
   such as MH-E, NMH, exmh.  Experimentally supported by UW-IMAP
   [http://www.washington.edu/imap/].
 * <MMDF> [MailboxFormat.MMDF.txt]: Similar to mbox, but instead of From-line
   separators it uses four '^A' characters
 * <Cyrus> [MailboxFormat.Cyrus.txt]: One file contains one message, plus there
   are a couple of index/cache files. Commonly referred to as being
   maildir-like, although they have only a single thing in common.

Adding support for new formats for Dovecot isn't very difficult, although it
can be time consuming. Dovecot exposes a nice and simple API which needs to be
implemented.

Software Support
----------------

+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+
| *Format/Software*             | *Dovecot                   | *UW-IMAP                           | *Courier-IMAP                       | *Exim                   | *Postfix                   | *PINE                              | *mutt                   | *procmail                   | *maildrop                               |
|                               | [http://www.dovecot.org/]* | [http://www.washington.edu/imap/]* | [http://www.courier-mta.org/imap/]* | [http://www.exim.org/]* | [http://www.postfix.org/]* | [http://www.washington.edu/pine/]* | [http://www.mutt.org/]* | [http://www.procmail.org/]* | [http://www.courier-mta.org/maildrop/]* |
+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+
| <mbox> [MailboxFormat.mbox.txt]| Yes                        | Yes                                | No                                  | Yes                     | Yes                        | Yes                                | Yes                     | Yes                         | Yes                                     |
+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+
| <mbx> [MailboxFormat.mbx.txt] | No                         | Yes                                | No                                  | Yes                     | No                         | Yes                                | No                      | No                          | No                                      |
+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+
| <maildir>                     | Yes                        | No                                 | Yes                                 | Yes                     | Yes                        | No                                 | Yes                     | Yes (3.22)                  | Yes                                     |
| [MailboxFormat.Maildir.txt]   |                            |                                    |                                     |                         |                            |                                    |                         |                             |                                         |
+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+
| <mailstore>                   | No                         | No                                 | No                                  | Yes                     | No                         | No                                 | No                      | No                          | No                                      |
| [MailboxFormat.mailstore.txt] |                            |                                    |                                     |                         |                            |                                    |                         |                             |                                         |
+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+
| <dbox> [MailboxFormat.dbox.txt]| Yes                        | No                                 | No                                  | No                      | No                         | No                                 | No                      | No                          | No                                      |
+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+
| <MH> [MailboxFormat.MH.txt]   | No                         | Yes                                | No                                  | No                      | No                         | Yes                                | Yes                     | Yes                         | No                                      |
+-------------------------------+----------------------------+------------------------------------+-------------------------------------+-------------------------+----------------------------+------------------------------------+-------------------------+-----------------------------+-----------------------------------------+

Conversion Between Mailbox Formats
----------------------------------

See <Migration.MailFormat.txt>.

References
----------

 * Mutt mailbox formats: http://rucus.ru.ac.za/docs/mutt/manual58.html
 * Article on mailbox formats: http://www.livejournal.com/users/rfunk/1571.html

 * Mbox and maildir comparison:
   http://www.linuxmail.info/mbox-maildir-mail-storage-formats/
   [http://www.linux-mail.info/mbox-maildir-mail-storage-formats/] 

(This file was created from the wiki on 2009-10-16 04:42)
