[Dovecot] Postfix user map

[Timo Sirainen]

http://hg.dovecot.org/dovecot-2.1/rev/f562bcaca215 implements "postmap" 
type sockets, which follow Postfix's tcp_table(5) protocol. So you can ask:

get user at domain

and Dovecot answers one of:

  - 200 1
  - 500 User not found
  - 400 Internal failure

So you can use this with Postfix:

virtual_mailbox_maps = tcp:127.0.0.1:1234

With Dovecot you can enable it with:

service auth {
   inet_listener postmap {
     listen = 127.0.0.1
     port = 1234
   }
}

Anyone have ideas if this could be improved, or used for some other 
purposes?