1. ISP are not known for hiring the most brilliant techy people. They bottom feed like any other employer, it's about keeping benefits and salaries low. If they have hired someone with more sense then an anvil, they are swamped with many many many other things and configuring an e-mail server is not at the top of their list.
2. E-Mail recipients... Oy! To say that a lot of them are dumber then box of rocks is to insult rocks, not to mention the box! Trying to explain to them that spammers are getting more and more sophisticated in their efforts is like trying to explain E=MC2 to my 6 year old. Trying to explain to them why you *really* need 13 different filters to try and snag all of the stuff they never want to see and at the same time trying to explain why there will be the occasional *false Positive* is even worse.
3. Personally, I am thinking plumber. I mean you still have to deal with peoples sh*&^ but at least it's simple sh*&^ and when you go home at night you are *done* for the day, and the pay is definitely better. The down sound is that it is not terribly intellectually challenging.