exim is far easier to comprehend for the administrator than sendmail. I have used exim for many years (as well as it's predecessor, smail, which I made small contributions to). I would like to see a standard exim rpm offered on Redhat. BTW, it's the standard MTA on Debian. There is an exim rpm available already. It was put together by Mark Bergsma <mark.nl>. I'm using it right now on RH6.1.
sendmail is the standard MTA on Red Hat.We can ship exim on the powertools, though