I’m not sure what the rate of other free e-mail service providers are, but Hotmail always has issues recognizing legitimate e-mail addresses.
For instance, here’s one from the epa.gov. How likely is it that someone who manages to have that domain, is going to do something against you?
It also doesn’t help that the largest e-mail provider in the world isn’t exactly liked by a government e-mail server.
Seriously, Microsoft? Come on. You can do better than this. I think I’ll start a series of “Hotmail False Positives” to show how ridiculous some of Hotmail’s worries are.