dummy IMAP server for when server has moved -

i'm moving mailserver (imap).

in last century, when using pop3, made script allowed login, , fetch message saying "hey, update settings".

now, using imap, seems little more complicated... there simple dummy imapd server available that?

or script (netcat?) can collect usernames, can contact few remaining users?

in theory simplest of scripts do:

#!/bin/sh echo '* ok [alert] mail has moved, ask leif' echo '* bye' 

in practice alert may or may not displayed users.

capturing login names more complicated , perhaps not worth trouble.