[Dovecot] Maildir "locking"

[Attila Nagy]

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?

Thanks,