[Dovecot] Maildir "locking"

[Timo Sirainen]

On Wed, 2011-09-14 at 13:32 +0200, Attila Nagy wrote:
> Hello,
> 
> I'm looking for the alternative of qmail's chmod -t (sticky bit on the 
> maildir root) for Dovecot. What I'm trying to achieve with this lock:
> - Dovecot lmtp should give back a temporary error (so the email will be 
> deferred and re-delivered later)
> - all other Dovecot daemons (pop, imap) should work as usual, but should 
> not alter maildir contents (they can modify their own files, like 
> indexes, logs etc)
> 
> What is the best way to do this? If there is no such thing currently, 
> would it be hard to implement the sticky bit checking on the root?

dovecot-uidlist.lock basically does this. Dovecot comes with maildirlock
utility to properly create it. How long would your locks be? They are
assumed stale after 2 minutes if you don't update the mtime. Readers
will block and if they're still locked after 2 minutes they'll abort (if
mtime has been changed). There's also mail_max_lock_timeout setting that
changes this wait (you could e.g. lower it only with lmtp).