Quota
=====

Quota backend specifies the method how Dovecot keeps track of the current quota
usage. They don't (usually) specify users' quota limits, that's done by
returning extra fields from userdb. There are different quota backends that
Dovecot can use:

 * <fs> [Quota.FS.txt]: Filesystem quota.
 * <dirsize> [Quota.Dirsize.txt]: The simplest and slowest quota backend, but
   it works quite well with mboxes.
 * <dict> [Quota.Dict.txt]: Store quota usage in a dictionary (e.g. SQL).
 * <maildir> [Quota.Maildir.txt]: Store quota usage in Maildir++ maildirsize
   files. This is the most commonly used quota for virtual users.

Enabling quota plugins
----------------------

There are currently two quota related plugins:

 * quota: Implements the actual quota handling and includes also all the quota
   backends.
 * imap_quota: For reporting quota information via IMAP.

Usually you'd enable these by adding them to the 'mail_plugins' settings in the
config file:

---%<-------------------------------------------------------------------------
protocol imap {
  mail_plugins = quota imap_quota
}
protocol pop3 {
  mail_plugins = quota
}
# In case you're using deliver:
protocol lda {
  mail_plugins = quota
}
---%<-------------------------------------------------------------------------

Configuration
-------------

The configuration is done differently for v1.0 and v1.1:

 * <v1.0 quota configuration> [Quota.1.0.txt]
 * <v1.1 quota configuration> [Quota.1.1.txt]

Quota and Trash mailbox
-----------------------

Standard way to expunge messages with IMAP works by:

 1. Marking message with \Deleted flag
 2. Actually expunging the message using EXPUNGE command

Both of these commands can be successfully used while user's quota is full.
However many clients use a "move-to-Trash" feature, which works by:

 1. COPY the message to Trash mailbox
 2. Mark the message with \Deleted
 3. Expunge the message from the original mailbox.
 4. (Maybe later expunge the message from Trash when "clean trash" feature is
    used)

If user is over quota (or just under it), the first COPY command will fail and
user may get an unintuitive message about not being able to delete messages
because user is over quota. The possible solutions for this are:

 * Disable move-to-trash feature from client
 * Dovecot v1.0 + <Maildir++> [Quota.Maildir.txt] quota: You can completely
   ignore Trash mailbox from quota calculation by appending ':ignore=Trash' to
   the quota line. Note that this would allow users to store messages
   infinitely to the mailbox.
 * Dovecot v1.1 or <v1.0 quota rewrite> [Quota.1.1.txt]: You can ignore Trash
   like with v1.0, but you can also give a separate quota rule giving Trash
   mailbox somewhat more quota (but not unlimited).

To make sure users don't start keeping messages permanently in Trash you can
use a nightly <cronjob or expire plugin (v1.1)> [Plugins.Expire.txt] to expunge
old messages from Trash mailbox.

(This file was created from the wiki on 2010-06-01 04:42)
