Discussion on MTA : SendMail, Postfix, Exim, Qmail
MTA Comparison
For historical reasons the most popular continues to be sendmail but since there are safer alternatives do not think that would be the case that some distro courageous thought to their use by default?
Especially for distro think for security as openbsd.
Which you prefer between postfix and exim?
Qmail.
I think that still has the drawback of do not be a truly open.