On the topic of filters: I have over 200. It's more reliable than spam filtering (in the sense that I know I wont ever get an email from them again, and I don't

On the topic of filters: I have over 200. It's more reliable than spam filtering (in the sense that I know I wont ever get an email from them again, and I don't have to worry about if that link is going to put my email on some "verified" to-spam list). So I doubt filters have anything to do with it ;) That's all handled on Google's backend. On a side note, I do recall a few theories that were related to account age. Accounts opened around the same time seemed to be affected (as I read, anyway). This is a possible situation, however, it's almost impossible to know for sure.