I love exim4 – and i cannot get on with either postfix or sendmail. The level of sophistication that is required these days to set up a trouble-free email server is, i believe, matched only by exim4's sophistication and ease-of-setup
Read here how to do it
postfix is great – and secure – and lovely – but if you need a rocket wizard to configure it, then it's not much good to anybody. And sendmail is just… my hat off to anyone who can configure sendmail because it's just… just… absolutely fine for anyone who has an IQ of above 160. So, finally, having got a setup that i am finally happy with, that can cope with several domains, i thought it was time to let people know about it.