Maildir configuration
=====================

See <MailboxFormat.Maildir.txt> for a complete description of how Dovecot has
implemented Maildir support.

Mail location
-------------

Maildir exists almost always in '~/Maildir' directory. The mail location is
specified with:

---%<-------------------------------------------------------------------------
mail_location = maildir:~/Maildir
---%<-------------------------------------------------------------------------

Directory layout
----------------

By default Dovecot uses Maildir++ directory layout. This means that all
mailboxes are stored in a single directory and prefixed with a dot. For
example:

 * Maildir/.folder
 * Maildir/.folder.subfolder

If you want maildirs to use hierarchical directories, such as:

 * Maildir/folder/
 * Maildir/folder/subfolder/

you'll need to enable fs layout:

---%<-------------------------------------------------------------------------
# v1.1+ only:
mail_location = maildir:~/Maildir:LAYOUT=fs
---%<-------------------------------------------------------------------------

Control files
-------------

Dovecot stores some Maildir metadata into two control files:

 * 'dovecot-uidlist' file contains IMAP UID <-> Maildir filename mapping
 * 'dovecot-keywords' file contains Maildir filename flag (a..z = 0..25) <->
   keyword name mapping

Both of these files are described fully in <MailboxFormat.Maildir.txt>. The
important thing to remember about them however is that they shouldn't be
treated the same way as index files. Index files can be deleted and rebuilt
without any side effects, but if you delete control files you'll cause messages
to get new UIDs and possibly lose keyword names.

If the messages get new UIDs, the IMAP clients will invalidate their local
cache and download the messages all over again. If you do this for all the
users, you could cause huge disk I/O bursts to your server.

Dovecot can't currently handle not being able to write the control files, so it
will cause problems with <filesystem quota> [Quota.FS.txt]. To avoid problems
with this, you should place control files into a partition where quota isn't
checked. You can specify this by adding ':CONTROL=<path>' to 'mail_location',
for example:

---%<-------------------------------------------------------------------------
mail_location = maildir:~/Maildir:CONTROL=/var/no-quota/%u
---%<-------------------------------------------------------------------------

Index files
-----------

See <MailLocation#indexfiles> [MailLocation.txt] for full explanation of how to
change the index path. For example:

---%<-------------------------------------------------------------------------
mail_location = maildir:~/Maildir:INDEX=/var/indexes/%u
---%<-------------------------------------------------------------------------

Optimizations
-------------

 * 'maildir_very_dirty_syncs=yes' (v1.2+): Assume that only Dovecot accesses
   'cur/' directory. If another process (or even Dovecot which doesn't update
   index files) does changes to 'cur/' while the mailbox is simultaneously
   being modified by Dovecot, Dovecot may not notice those external changes.
   It's still safe to deliver new mails to 'new/' using non-Dovecot software.
 * 'maildir_copy_with_hardlinks=yes' (default in v1.1+): When copying a
   message, do it with hard links whenever possible. This makes the performance
   much better, and it's unlikely to have any side effects. This will be
   default in some future version. The only downside is that copying to a
   shared mailbox may cause permission problems.
 * 'maildir_stat_dirs=no' (default): Assume that all the files beginning with a
   dot in the maildir are maildirs. You shouldn't have any non-directory files
   beginning with a dot in the maildirs, but if you do you may need to set this
   to "yes", in which case Dovecot needs to stat() each directory entry, which
   degrades the performance. Some filesystems provide the
   directory/non-directory status for free without having to stat(). In those
   filesystems this setting is ignored.
 * 'maildir_copy_preserve_filename = yes' (not default): When copying a
   message, try to preserve the base filename. This may allow you to optimize
   your backups, but other than that it gives no benefits. NOTE: This setting
   requires 'maildir_copy_with_hardlinks = yes' to work.

Filesystem optimizations
------------------------

See "Maildir and filesystems" section in <MailboxFormat.Maildir.txt>.

(This file was created from the wiki on 2011-05-11 04:42)
