I once read something that become engraved in my mind until today; it said:
"No one can consider it self a sysadmin until has configured properlly a sendmail once. And he must be totally insane if he does it again".
There is some amount ou truth in it, anyway.
Nowdays, with m4 and IDA the configuration of sendmail is rather easy as the configuration tools write the sendmail.cf file for us.
And another reason is the book I purchased some years ago that has everything that there is about sendmail, book which I couldn't find equivalent to other MTAs (like postfix or qmail).
I do like postfix but I think that there is still necessary a lot of time until I master it (as the time to study is always the time thare stays left....)
And, the truth is, sendmail is powerfull. That's where the complexity cames from.
About security, is has improved a lot over the years and, in fact, sendmail is old code, mainly. So it's stable.
But it has its issues (like normally anytjing has) and I've been learning to know them.
I would like to know postfix better but, so far, I couldn't find a book equivalent to the one I have about sendmail.
(Probably, I just didn't find it yet, if it has already been written). But I'll keep up looking.
And I would like to have more time just to study and learn...
In fact, that's the most usefull time one can have!
Well, back to work!