A while back, I realized I've missed lots and lots of important mails during about four months - Gmail had suddenly started flagging completely legit mail as sp

A while back, I realized I've missed lots and lots of important mails during about four months - Gmail had suddenly started flagging completely legit mail as spam, even from people I've had contact with previously. I tried flagging those mails appropriately, moved them to the inbox, but that didn't help either. Finally, I wrote a complaint feedback message, and a few days later, my spam filter was back to normal. I assume they put a small fraction of their users in A/B tests for the spam filter and can remove you manually on request. If that is true, it's completely unacceptable. I should probably migrate soon.