I really like the idea of setting your MX record to 127.0.0.1. I am not sure what problems this causes (the author mentions people are angry about it) but I like it.

This makes me realize that DNS is slightly flawed in that you can prove "the owner of example.com wants to accept email at X.Y.Z.A" but not "the owner of X.Y.Z.A wants to accept email for example.com". (My experience using a managed load balancer on Amazon was that I got a ton of traffic for websites that weren't mine. Some DNS record must have been out there pointing towards our IP, which I guess is bound to happen when you only have 2^32 of them to share among all of humanity. Someone should do something about that...)