When setting up a Cyrus IMAP server and you want to use a MySql database to hold user names and passwords, you must use the mysql module for PAM to authenticate because it can handle passwords that are stored using crypt ( the ENCRYPT function in mysql ). While there is also the aux_prop plugin that supports looking the information up from the same source, it does not support crypt without patching. Especially if you'd rather install from packages than from the source code - ie, your time is valuable.