Dovecot, enforcing retention policy

From Ubuntuwiki.net

If you need to enforce document retention policies on a Dovecot IMAP server, you can use the Lazy Expunge plugin to cause any mail or mailbox which has been deleted to be moved into a different namespace rather than actually deleted from the server.

With this configuration (which can simply be appended to the end of the existing dovecot.conf), an expunged_messages folder and a deleted_mailboxes folder will be created in /data/vmail, and they will contain exactly what it sounds like. In addition, an expunged_messages folder inside the deleted_mailboxes folder will be created if anybody should ever actually view one of the deleted mailboxes using dovecot, and expunge a message from it.

### LAZY_EXPUNGE CONFIGS

# the default namespace
namespace private {
  prefix =
  separator = /
  inbox = yes
}

# namespaces for lazy_expunge plugin:
namespace private {
  prefix = .EXPUNGED/
  separator = /
  location = maildir:/data/vmail/expunged_messages/%d/%n/Maildir
  hidden = yes
  list = no
}
namespace private {
  prefix = .DELETED/
  separator = /
  location = maildir:/data/vmail/deleted_mailboxes/%d/%n/Maildir
  hidden = yes
  list = no
}
namespace private {
  prefix = .DELETED/.EXPUNGED/
  separator = /
  location = maildir:/data/vmail/deleted_mailboxes/expunged_messages/%d/%n/Maildir
  hidden = yes
  list = no
}

protocol imap {
  mail_plugins = lazy_expunge
}

plugin {
  lazy_expunge = .EXPUNGED/ .DELETED/ .DELETED/.EXPUNGED/
}