Just thought I'd share this... after using it privately for some time at my
own site, I have now released:
smtpauth - Authenticating proxy for servers without SMTP AUTH
Let's say that you already have a functioning SMTP server which doesn't
support encryption or authentication, and for whatever reason you don't
want to recompile it with that massive Cyrus package. My software (in
conjunction with stunnel for the SSL wrapping on port 465) can allow
clients to connect and authenticate using PLAIN or LOGIN methods, while
your real SMTP server doesn't have to know anything about authentication.
It's worked quite well with the various mail clients used at our site, and
Postfix and Sendmail.
This same software can also be used to create an authenticated submission
service on cleartext port 587 with plain old inetd. Instructions included.
This is meant for small sites only. You have to create a file containing
plaintext usernames and passwords so there is a major risk there. The
software does log your logins, and also inserts the actual client IP
address into mail headers for easier tracking.