A few years ago I had an argument with a "professional" from another NOC concerning the proper repair for his outgoing-mail-bouncing-off-of-my-firewall issue. When I suggested that he repair the reverse lookups in his external DNS's, he snapped and stated that he was an (DNS) expert because he had his MCSE. He stated that I was the fifth NOC that had told him that (there's a clue in there somewhere) and that we should all get our acts together and turn off reverse lookups for SMTP.
To get a description of the day that I've had, just re-read the words in red above. I'll laugh later.