@Logicfest -- there are a lot of legitimate reasons to use anonymous email addresses. People do have an interest in protecting their privacy online, after all.
And, there are a lot of great services out there that are seen as legitimate and are not blocked by spam filters. If you'd like to test and see if those are screened, subscribe to one and send a test to your regular email account. If it gets through, the chances are good you've got a server that is viewed as legitimate.