Which is the post popular one and why? I know Cpanel uses Exim. And Ala hosts use sendmail. But what is the difference between the three?

Have a look at:
http://www.patoche.org/LTT/email/00000159.html

That was interesting. Thanx for the link :)

Some of "problems" expressed in Qmail are dated in that document. I believe QMail supports SPAM filtering and RBL now.

This is true. I use qmail to handle all my clients e-mail. As of yet, we have zero reports of it loosing mail, security problems or anything like that.

It is also fairly easy to setup provided you read the docs and go step by step.

Ok.. Sendmail = buggy as HELL . I absolutely LOVE qmail so its a little biased opinion but I say go with qmail with vpopmail.

James R. Clark II
Nethosters Inc.
http://www.nethosters.com

We use qmail, it is probablly the best mail package with Vpopmail ever. Very secure, very fast, support virus scanning, RBL, Spam Filtering, and alot more.

You may also check:

http://www.linuxplanet.com/linuxplanet/reviews/1640/1/

And don't forget:

http://www.linuxworld.com/linuxworld/expo/lw-email.html

:)

Thanx guys :)