See http://wiki.dovecot.org/Quota/Configuration for more details.

mail_plugins = $mail_plugins quota

Enable quota plugin for tracking and enforcing the quota.

protocol imap {
  mail_plugins = $mail_plugins imap_quota

Enable the IMAP QUOTA extension, allowing IMAP clients to ask for the current quota usage.

plugin {
  quota = count:User quota

Track the current quota usage in Dovecot’s index files.

plugin {
  quota_vsizes = yes

Required by quota=count backend. Indicates that the quota plugin should use virtual sizes rather than physical sizes when calculating message sizes.

  quota_max_mail_size = 100M

Controls the maximum message size that is allowed to be saved (e.g. by LMTP, IMAP APPEND or doveadm save).

The default is 0, which is unlimited. Setting this is especially useful with obox, because a single huge mail could eat all of the fscache causing problems in the server globally.

This setting should usually be set to about the same size as the maximum allowed incoming and/or outgoing mail size on on the MTA.

  quota_warning = storage=100%% quota-warning 100 %u
  quota_warning2 = storage=95%% quota-warning 95 %u
  quota_warning3 = -storage=100%% quota-warning below %u

Configure quota warning scripts to be triggered at specific sizes. Note that %% needs to be written twice to avoid %variable expansion. For example, at 95% usage a warning email could be sent to user. At 100% an external SMTP database could be updated to reject mails directly.

At -100% user again has more quota available and the SMTP database can be updated to allow mails again. The quota-warning means to connect to the quota-warning UNIX socket, which is a Dovecot script service described below.


obox installations using quota_over_script must currently also have quota_over_flag_lazy_check=yes enabled. Otherwise the quota_over_flag checking may cause a race condition with metacache cleaning, which may end up losing folder names or mail flags within folders.

service quota-warning {
  executable = script /usr/local/bin/quota-warning.sh
  user = vmail
  unix_listener quota-warning {

Example quota-warning service which executes quota-warning.sh script.

You may also want to use quota_clone plugin to keep track of all the users’ quotas in an efficient database. (It’s very slow to query every user’s quota from the index files directly.) See http://wiki.dovecot.org/Plugins/QuotaClone

Debugging Quota

User’s current quota usage can be looked up with: doveadm quota get -u user@domain

User’s current quota may sometimes be wrong for various reasons (typically only after some other problems). The quota can be recalculated with:

doveadm quota recalc -u user@domain