I use MySQL to store user data in courier. Here’s how to set it up. Configure Courier Before you begin, find your courier installation’s configuration directory. It is usually /usr/local/etc/courier, /etc/courier or /usr/local/courier/etc. Unless otherwise noted, the files mentioned here will be in this directory. smtpaccess/ You need to edit the files in this directory to allow relaying by IP address. To allow an IP to relay, add a line like this to any file in this directory.
Like many people, I setup courier to use mysql for authentication. When I went through the setup, I decided to store username as [email protected] in the accounts table. Users who are not in the default domain, can login as [email protected] and they are good to go. This works well in most modern email clients, but some older clients, notably Netscape 4.5, can’t use this syntax and are unable to login.