Re: and I remember vaguely
I use sendmail with an IMAP server (I use Cyrus but I set it up over a decade ago and it just works). Other solutions obviously exist. This one seemed just fine when I set it up. Integrating Cyrus was pretty easy. I'm using the FreeBSD version of sendmail.
No need for bloat-ness and security craters, like Micros~1 Exchange