
Delayed Expunge
***************

When a user or IMAP client expunges a message or an entire folder,
messages become unavailable to the user.

When the deletion is accidental, administrators may have to recover
the messages from some place. When the messages are purposefully
deleted, the user may have done so not with the best of intentions.

In any case, the time between a message arriving and being deleted may
not be sufficient to ensure the message is replicated, included in the
next backup cycle, and generally available for recovery or compliance
with the regulatory environment.

Cyrus IMAP introduces *delayed expunge*, which ensures message files
are not immediately unlinked from the filesystem, and instead makes
purging the message files from the filesystem a separate event.

This enables administrators to quickly recover access to messages that
have been accidentally deleted, as well as allows the environment to
ensure messages remain available for includion in the next backup
cycle.


Configuring Cyrus IMAP for Delayed Expunge
==========================================

To enable or disable Delayed Expunge, please check the following
settings in imapd.conf(5).

      "expunge_mode:" delayed

         The mode in which messages (and their corresponding cache
         entries) are expunged.  "default" mode is the old behavior in
         which the message files are purged at the time of the
         EXPUNGE, but index and cache records are retained to
         facilitate QRESYNC.  (Note that this behaviour is no longer
         the default, but is so named for historical reasons.)  In
         "delayed" mode, which is the default since Cyrus 2.5.0, the
         message files are also retained, allowing unexpunge to rescue
         them.  In "immediate" mode, both the message files and the
         index records are removed as soon as possible.  In all cases,
         nothing will be finally purged until all other processes have
         closed the mailbox to ensure they never see data disappear
         under them.  In "default" or "delayed" mode, a later run of
         "cyr_expire" will clean out the retained records (and
         possibly message files). This reduces the amount of I/O that
         takes place at the time of EXPUNGE and should result in
         greater responsiveness for the client, especially when
         expunging a large number of messages. Allowed values:
         *default*, *immediate*, *delayed*

See also:

  * unexpunge

  * Delayed Delete

  * When is What ... Deleted, Expired, Expunged or Purged?

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