I have been running my own mail server for a number of years. I recently was forced to move to a new IP. I had to get my server listed on DNSWL, then send in ma

I have been running my own mail server for a number of years. I recently was forced to move to a new IP. I had to get my server listed on DNSWL, then send in manual requests to Microsoft, AOL, and Yahoo to not block my email because they all seem to deny by default. I also ran through a couple of IPs with my provider before I found one that wasn't on any meaningful RBLs (my IP's on SpamGrouper, but that list is clearly run by an insane person and nobody seems to use it). As other people point out, some mail providers are just complete assholes and will blackhole your mail with no indication to the sender or recipient that it happened.