Cyrus IMAP features a flexible Quota scheme with support for limiting various resources, such as storage or number of folders or messages.
Controlling Quota Behavior¶
How restrictive quotas will be may be tailored to the needs of different sites, via the use of several settings in imapd.conf(5):
lmtp_over_quota_perm_failure:0If enabled, lmtpd returns a permanent failure code when a user’s mailbox is over quota. By default, the failure is temporary, causing the MTA to queue the message and retry later.
lmtp_strict_quota:0If enabled, lmtpd returns a failure code when the incoming message will cause the user’s mailbox to exceed its quota. By default, the failure won’t occur until the mailbox is already over quota.
quotawarn:90The percent of quota utilization over which the server generates warnings.
quotawarnkb:0The maximum amount of free space (in kB) at which to give a quota warning (if this value is 0, or if the quota is smaller than this amount, then warnings are always given).
quotawarnmsg:0The maximum amount of messages at which to give a quota warning (if this value is 0, or if the quota is smaller than this amount, then warnings are always given).
If set to a value of zero or higher, users have their INBOX folders created upon a successful login event or upon lmtpd(8) message delivery if autocreate_post is enabled, provided their INBOX did not yet already exist.
The user’s quota is set to the value if it is greater than zero, otherwise the user has unlimited quota.
Note that quota is specified in kilobytes.
If set to a value of zero or higher, users who have their INBOX folders created upon a successful login event (see autocreate_quota), or upon lmtpd(8) message delivery if autocreate_post is enabled, receive the message quota configured in this option.
The default of -1 disables assigning message quota.
For consistency with autocreate_quota, a value of zero is treated as unlimited message quota, rather than a message quota of zero.
Quota information is stored either in a database (i.e. twoskip,
skiplist) or in “quotalegacy” format, which is a filesystem hierarchy.
This is controlled by the
quota_db setting in
imapd.conf(5). Here’s more about the pertinent settings:
The cyrusdb backend to use for quotas.
Allowed values: flat, skiplist, sql, quotalegacy, twoskip, lmdb
quota_db_path:<none>The absolute path for the quota database (if you choose a single-file quota DB type - or the base path if you choose quotalegacy). If not specified will be confdir/quotas.db or confdir/quota/
Converting Quotas Database¶
The cvt_cyrusdb(8) utility may be used to convert between
formats. It’s usage with
quotalegacy is a special case, in that
the first argument (“<old db>”) will be the path to the base of the
quotalegacy directory structure, not to a particular file.
For example, given this typical layout:
/var/lib/imap/ | /quota/ | /A/ | /user/ | /bob/
cvt_cyrusdb command would be:
cvt_cyrusdb /var/lib/imap/quota quotalegacy /var/lib/imap/quotas.db twoskip
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