The following list is an index of various tools and methods to use for SMTP Authentication. For example, if you would like to use MySQL for authenticating your exim users, click on the link "MySQL."
pwauth (easily authenticate against /etc/shadow without running as root)
Broken Clients - Non-standard EHLO response
Authenticated Forwarding - Using exim for authentication on smart relays
How to make custom authenticators, e.g. for CRAM-SHA1
Testing authentication - SMTP Client can be found at http://www-uxsup.csx.cam.ac.uk/~fanf2/hermes/src/smtpc/