Quota Configuration
===================

Contents


 1. Quota Configuration

     1. Quota rules

         1. Limit configuration

     2. Per-user quota

         1. LDAP

         2. MySQL

         3. PostgreSQL, SQLite

         4. passwd-file

         5. passwd

     3. Quota for public namespaces

     4. Quota for private namespaces

     5. Custom Quota Exceeded Message

     6. Quota warnings

     7. Overquota-flag (v2.2.16+)

     8. Quota grace

     9. Maximum saved mail size

     10. Quota admin commands

The configuration is split into multiple settings:

First you have the quota root backend configuration. Quota root is a concept
from IMAP Quota specifications [http://www.rfc-editor.org/rfc/rfc2087.txt].
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 others (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 root configuration includes the backend name, quota root name and its
parameters, if there are any:

---%<-------------------------------------------------------------------------
quota = <backend>[:<quota root name>[:<backend args>]]
---%<-------------------------------------------------------------------------

The quota root name is just an arbitrary string that is sent to IMAP clients,
which in turn may show it to the user. The name has no meaning. By default an
empty string is used, but you may want to change that since some clients (Apple
Mail) break and don't show quota at all then.

You can define multiple quota roots by appending an increasing number, for
example:

---%<-------------------------------------------------------------------------
plugin {
  quota = maildir:User quota
  quota2 = fs:Disk quota
  #quota3 = ...
}
---%<-------------------------------------------------------------------------

Quota rules
-----------

Quota rules configure the actual quota limits. The syntax is:

---%<-------------------------------------------------------------------------
quota_rule = <mailbox name>:<limit configuration>
#quota_rule2 = ...
#quota_rule3 = ..etc..
---%<-------------------------------------------------------------------------

"*" as the mailbox name configures the default limit, which is applied on top
of a mailbox-specific limit if found. So for 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.

"?" as the mailbox name works almost like "*". The difference is that "?" is
used only if quota backend doesn't override the limit. For example with
Maildir++ [http://www.inter7.com/courierimap/README.maildirquota.html] quota if
'maildirsize' file exists the limits are taken from it, but if it doesn't exist
the "?" limits are used.

"*" can't be used as a generic wildcard in mailbox names, so for example "box*"
wouldn't match "boxes". As shown in the above example, the first quota rule is
named 'quota_rule' while the following rules have an increasing digit in them.
You can have as many quota rules as you want.

Limit configuration
-------------------

The following limit names are supported:

 * *storage*: Quota limit in kilobytes, 0 means unlimited.
 * *bytes*: Quota limit in bytes, 0 means unlimited.
 * *messages*: Quota limit in number of messages, 0 means unlimited. This
   probably isn't very useful.
 * *backend*: Quota backend-specific limit configuration.
 * *ignore*: Don't include the specified mailbox in quota at all.

All of these support also b/k/M/G/T/% suffixes. So storage=100M and bytes=100M
both mean the exact same thing. messages=1k also means 1024 messages (not
1000).

Percents are relative to the default rule. For example:

---%<-------------------------------------------------------------------------
plugin {
  quota = maildir:User quota
  quota_rule = *:storage=1GB
  # 10% of 1GB = 100MB
  quota_rule2 = Trash:storage=+10%%
  # 20% of 1GB = 200MB
  quota_rule3 = Spam:storage=+20%%
}
---%<-------------------------------------------------------------------------

Note that % is written twice to escape it, because <%variables> [Variables.txt]
are expanded in plugin section. <userdb> [UserDatabase.txt] configuration may
or may not require this escaping.

Backend-specific configuration currently is used only with Maildir++ quota
backend. It means you can have the quota in Maildir++ format (e.g.
"10000000S").

Per-user quota
--------------

You can override quota rules in your <userdb> [UserDatabase.txt]'s <extra
fields> [UserDatabase.ExtraFields.txt]. Keep all the global settings in 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 <userdb static> [UserDatabase.Static.txt].
 * 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 <userdb ldap>
[AuthDatabase.LDAP.txt].

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'
---%<-------------------------------------------------------------------------

Remember that 'user_query' is used only if you use <userdb sql>
[AuthDatabase.SQL.txt].

PostgreSQL, SQLite
------------------

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

Remember that 'user_query' is used only if you use <userdb sql>
[AuthDatabase.SQL.txt].

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> [AuthDatabase.Passwd.txt] 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 <userdb passwd-file>
[AuthDatabase.PasswdFile.txt].

Quota for public namespaces
---------------------------

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

---%<-------------------------------------------------------------------------
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 you could have something like:

---%<-------------------------------------------------------------------------
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, the '%u.default' tracks the quota of other
folders. See <Variables.txt> for further help on variables.

Custom Quota Exceeded Message
-----------------------------

You can configure Dovecot to send a custom string instead of the default quota
exceeded message. You could have something like:

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

Dovecot can also read the quota exceeded message from a file:

---%<-------------------------------------------------------------------------
plugin {
   quota_exceeded_message = </path/to/quota_exceeded_message.txt
}
---%<-------------------------------------------------------------------------

Quota warnings
--------------

You can configure Dovecot to run an external command when user's quota exceeds
a specified limit. Note that the warning is ONLY executed at the exact time
when the limit is being crossed, so when you're testing it you have to do it by
crossing the limit by saving a new mail. If something else besides Dovecot
updates quota so that the limit is crossed, the warning is never executed. The
syntax is:

---%<-------------------------------------------------------------------------
quota_warning = <limit configuration> <quota-warning socket name> <parameters>
#quota_warning2 = ...
#quota_warning3 = ..etc..
---%<-------------------------------------------------------------------------

Limit configuration is almost exactly same as for rules, with the exception of
adding "-" before the value for "reverse" warnings where the script is called
when quota drops below the value. Usually you want to use percents instead of
absolute limits. Only the command for the first exceeded limit is executed, so
configure the highest limit first. The actual commands that are run need to be
created as services.

An 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 (v2.2.16+)
-------------------------

Quota warnings 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. The only
problem with this has been that 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 get solved 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". There are two
settings to configure what to do:

---%<-------------------------------------------------------------------------
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 = *

  # If set, overquota-flag is checked only when current quota usage is going to
be checked anyway.
  # This can be used to optimize this check in case it's running too slowly.
(v2.2.25+)
  #quota_over_flag_lazy_check = yes

  # Service script to execute if overquota-flag is wrong. Configured the
  # same as quota_warning scripts. The current quota_over_flag's value is
  # appended as the last parameter.
  quota_over_script = quota-warning mismatch %u
}
---%<-------------------------------------------------------------------------

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
-----------------------

(v2.2.29+) 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 size, 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 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 dic_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)
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2019-06-19 12:42)