What's the command line for preauth IMAP using Dovecot? Many sites give:
dovecot --exec-mail imap But on my system this returns:
Usage: dovecot [-F] [-c <config file>] [-p] [-n] [-a] [--help] [--version] [--build-options] [reload] [stop] Fatal: Unknown argument: --exec-mail 
dovecot --exec-mail imap is not a valid command line switch in recent releases of Dovecot. There is now a separate binary named simply "imap" which launches a pre-authenticated IMAP session.
Source of information: Dovecot's upgrading to 2.0 instructions
On Ubuntu, this binary is not in the default path, it's located at /usr/lib/dovecot/imap