Quota Configuration

See Quota Plugin for an overview of the Dovecot quota plugin.

Quota configuration is split into multiple settings: quota root and quota rules.

Settings

See quota-plugin for all quota settings.

Quota Root

See quota for the details on the syntax of the quota root setting.

Quota root is a concept from IMAP Quota specifications (RFC 2087). Normally you’ll have only one quota root, but in theory there could be, e.g., “user quota” and “domain quota” roots. It’s unspecified how the quota roots interact with each other (if at all). In some systems, for example, INBOX could have a completely different quota root from the rest of the mailboxes (e.g. INBOX in /var/mail/ partition and others in /home/ partition).

Quota Rules

See quota for the details on the syntax of the quota rule setting.

For Maildir++ quota if maildirsize file exists the limits are taken from it but if it doesn’t exist the ? limits are used.

Example

quota_rule = *:storage=1G
quota_rule2 = Trash:storage=+100M
quota_rule3 = SPAM:ignore

This means that the user has 1GB quota, but when saving messages to Trash mailbox it’s possible to use up to 1.1GB of quota. The quota isn’t specifically assigned to Trash, so if you had 1GB of mails in Trash you could still save 100MB of mails to Trash, but nothing to other mailboxes. The idea of this is mostly to allow the clients’ move-to-Trash feature work while user is deleting messages to get under quota. Additionally, any messages in the SPAM folder are ignored per the ignore directive and would not count against the quota.

The first quota rule muse be named quota_rule while the following rules have an increasing digit in them. You can have as many quota rules as you want.

Per-User Quota

You can override quota rules in your User database extra fields. Keep global settings in configuration plugin section and override only those settings you need to in your userdb.

If you’re wondering why per-user quota isn’t working:

• Check that dovecot-lda is called with -d parameter.

• Check that you’re not using Static User Database.

• Check that quota_rule setting is properly returned by userdb. Enable auth_debug = yes and mail_debug = yes to see this.

For example:

plugin {
  quota = maildir:User quota
  quota_rule = *:storage=1G
  quota_rule2 = Trash:storage=+100M
}

Next override the default 1GB quota for users:

LDAP

Quota limit is in quotaBytes field:

user_attrs = homeDirectory=home, quotaBytes=quota_rule=*:bytes=%$

Remember that user_attrs is used only if you use LDAP Authentication.

SQL

Example (for MySQL):

user_query = SELECT uid, gid, home, \
  concat('*:bytes=', quota_limit_bytes) AS quota_rule \
  FROM users WHERE userid = '%u'

# MySQL with userdb prefetch: Remember to prefix quota_rule with userdb_
# (just like all other userdb extra fields):
password_query = SELECT userid AS user, password, \
  uid AS userdb_uid, gid AS userdb_gid, \
  concat('*:bytes=', quota_limit_bytes) AS userdb_quota_rule \
  FROM users WHERE userid = '%u'

Example (for PostgreSQL and SQLite):

Remember that user_query is used only if you use SQL.

user_query = SELECT uid, gid, home, \
  '*:bytes=' || quota_limit_bytes AS quota_rule \
  FROM users WHERE userid = '%u'

passwd-file

Example Passwd-file entries:

user:{plain}pass:1000:1000::/home/user::userdb_quota_rule=*:bytes=100M
user2:{plain}pass2:1001:1001::/home/user2::userdb_quota_rule=*:bytes=200M
user3:{plain}pass3:1002:1002::/home/user3::userdb_mail=maildir:~/Maildir userdb_quota_rule=*:bytes=300M

passwd

The Passwd userdb doesn’t support extra fields. That’s why you can’t directly set users’ quota limits to passwd file. One possibility would be to write a script that reads quota limits from another file, merges them with passwd file and produces another passwd-file, which you could then use with Dovecot’s Passwd-file.

Quota for Public Namespaces

You can create a separate namespace-specific quota that’s shared between all users. This is done by adding :ns=<namespace prefix> parameter to quota setting. For example:

namespace {
  type = public
  prefix = Public/
  #location = ..
}

plugin {
  quota = maildir:User quota
  quota2 = maildir:Shared quota:ns=Public/
  #quota_rules and quota2_rules..
}

Quota for Private Namespaces

You can create a separate namespace-specific quota for a folder hierarchy. This is done by adding another namespace and the :ns=<namespace prefix> parameter to quota setting. For example:

namespace {
  type = private
  prefix = Archive/
  #location = ..
}

plugin {
  # Maildir quota
  quota = maildir:User quota:ns=
  quota2 = maildir:Archive quota:ns=Archive/

  # Dict quota
  #quota = dict:User quota:%u.default:ns=:proxy::quota
  #quota2 = dict:Archive quota:%u.archive:ns=Archive/:proxy::quota

  #quota_rules and quota2_rules..
}

Note: If you’re using dict quota, you need to make sure that the quota of the Archive namespace is calculated for another “user” than the default namespace. Either track different namespaces in different backends or make sure the users differs. %u.archive defines <username>.archive as key to track quota for the Archive namespace; %u.default tracks the quota of other folders. See Config Variables for further help on variables.

Quota and Shared Namespaces

Quota plugin considers shared namespaces against owner’s quota, not the current user’s. There is a limitation that per-user quota configuration is ignored, and the current user’s configuration is used.

Public namespaces are ignored unless there is explicit quota specified for it.

Custom Quota Exceeded Message

See quota_exceeded_message.

Example:

plugin {
  quota_exceeded_message = Quota exceeded, please go to http://www.example.com/over_quota_help for instructions on how to fix this.
}

Quota Warning Scripts

See quota_warning.

Example Configuration

plugin {
  quota_warning = storage=95%% quota-warning 95 %u
  quota_warning2 = storage=80%% quota-warning 80 %u
  quota_warning3 = -storage=100%% quota-warning below %u # user is no longer over quota
}

service quota-warning {
  executable = script /usr/local/bin/quota-warning.sh
  # use some unprivileged user for executing the quota warnings
  user = vmail
  unix_listener quota-warning {
  }
}

With the above example when user’s quota exceeds 80%, quota-warning.sh is executed with parameter 80. The same goes for when quota exceeds 95%. If user suddenly receives a huge mail and the quota jumps from 70% to 99%, only the 95 script is executed.

You have to create the quota-warning.sh script yourself. Here is an example that sends a mail to the user:

#!/bin/sh
PERCENT=$1
USER=$2
cat << EOF | /usr/local/libexec/dovecot/dovecot-lda -d $USER -o "plugin/quota=maildir:User quota:noenforcing"
From: postmaster@domain.com
Subject: quota warning

Your mailbox is now $PERCENT% full.
EOF

The quota enforcing is disabled to avoid looping. You’ll of course need to change the plugin/quota value to match the quota backend and other configuration you use. Basically preserve your original “quota” setting and just insert “:noenforcing” to proper location in it. For example with dict quota, you can use something like: -o "plugin/quota=dict:User quota::noenforcing:proxy::quota"

Overquota-flag

New in version v2.2.16.

Quota warning scripts can be used to set an overquota-flag to userdb (e.g. LDAP) when user goes over/under quota. This flag can be used by MTA to reject mails to an user who is over quota already at SMTP RCPT TO stage.

A problem with this approach is there are race conditions that in some rare situations cause the overquota-flag to be set even when user is already under quota. This situation doesn’t solve itself without manual admin intervention or the new overquota-flag feature: This feature checks the flag’s value every time user logs in (or mail gets delivered or any other email access to user) and compares it to the current actual quota usage. If the flag is wrong, a script is executed that should fix up the situation.

The overquota-flag name in userdb must be quota_over_flag.

These settings are available:

• quota_over_flag_lazy_check

• quota_over_flag_value

• quota_over_script

Example:

plugin {
  # If quota_over_flag=TRUE, the overquota-flag is enabled. Otherwise not.
  quota_over_flag_value = TRUE

  # Any non-empty value for quota_over_flag means user is over quota.
  # Wildcards can be used in a generic way, e.g. "*yes" or "*TRUE*"
  #quota_over_flag_value = *

  quota_over_flag_lazy_check = yes
  quota_over_script = quota-warning mismatch %u
}

Quota Grace

See quota_grace.

With v2.2+, by default the last mail can bring user over quota. This is useful to allow user to actually unambiguously become over quota instead of fail some of the last larger mails and pass through some smaller mails. Of course the last mail shouldn’t be allowed to bring the user hugely over quota, so by default in v2.2+ this limit is 10% of the user’s quota limit. (In v2.1 this is disabled by default.)

To change the quota grace, use:

plugin {
  # allow user to become max 10% over quota
  quota_grace = 10%%
  # allow user to become max 50 MB over quota
  quota_grace = 50 M
}

Maximum Saved Mail Size

New in version v2.2.29.

See quota_grace.

Dovecot allows specifying 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. Since outgoing mail sizes are also typically limited on the MTA side, it can be beneficial to prevent user from saving too large mails, which would later on fail on the MTA side anyway.

plugin {
  quota_max_mail_size = 100M
}

Quota Virtual Sizes

New in version v2.2.19.

See quota_vsizes.

Indicates that the quota plugin should use virtual sizes rather than physical sizes when calculating message sizes. Required for the count driver.

plugin {
  quota_vsizes = yes
}

Quota Admin Commands

The imap_quota plugin implements the SETQUOTA command, which allows changing the logged in user’s quota limit if the user is admin. Normally this means that a master user must log in with userdb_admin = y set in the master passdb. The changing is done via dict_set() command, so you must configure the quota_set setting to point to some dictionary where your quota limit exists. Usually this is in SQL, e.g.:

dovecot.conf:

plugin {
  quota_set = dict:proxy::sqlquota
}
dict {
  sqlquota = mysql:/etc/dovecot/dovecot-dict-sql.conf.ext
}

dovecot-dict-sql.conf.ext:

# Use "host= ... pass=foo#bar" with double-quotes if your password has '#'
# character.
connect = host=/var/run/mysqld/mysqld.sock dbname=mails user=admin \
  password=pass
# Alternatively you can connect to localhost as well:
#connect = host=localhost dbname=mails user=admin password=pass # port=3306

map {
  pattern = priv/quota/limit/storage
  table = quota
  username_field = username
  value_field = bytes
}
map {
  pattern = priv/quota/limit/messages
  table = quota
  username_field = username
  value_field = messages
}

Afterwards the quota can be changed with:

a SETQUOTA "User quota" (STORAGE 12345 MESSAGES 123)