Quick note on how to make alternative authentication modules work with Apache 2.2.
mod_auth_imap kept complaining about a missing password file:
(9)Bad file descriptor: Could not open password file: (null)
Turns out with Apache 2.2 you have to explicitly turn off Basic authentication even when you are using an alternative module. So a proper Apache 2.2
mod_auth_imap configuration would look something like this:
AuthBasicAuthoritative forces Apache to ignore the standard password file authentication.