We are currently researching the best way to go about switching our mail server (dovecot/postfix/debian 7) from local authentication to ldap (AD) authentication.
We would like to have local auth as backup as well during the transition. We could also use courier instead of dovecot if needed.
I am not looking for an answer here, I am just looking for advice from my fellow sysadmins on where to start. I have ldap auth working correctly with dovecot but I don't know how to make the local auth act as a backup.