I've wanted to try DSpam for a long time. Well today I finally installed it. I still have to actually use it, but I'm taking one step at a time. I'm a little annoyed that it appears that I have to use clamav with it, but whatever. More detailed notes about my experience with DSpam can be found at the DSpam page at Docunext.
I've also wanted to try Dovecot for a long time. I've heard really good things about it, but I just haven't had enough problems with Courier-IMAP to make the full switch.
Recently when exploring redundant eSMTP servers, I realized that Postfix requires SASL authentication, and went looking for a lightweight, dynamic back-end for saslauthd. Saslauthd can use a variety of back-ends, such as LDAP and IMAP authentication. I chose IMAP authentication, and then selected Dovecot as the IMAP server because it has a very flexible authentication system.
As I'm writing this, I'm coming to realize that NGINX is actually a more appropriate solution. Its authentication system is extremely simple and therefore flexible. I'll have to try it out!