The Gmail team recently launched[0] PostMaster tools[1]. I'm not sure if everyone has access, but maybe it would help?
[0] http://gmailblog.blogspot.com/2015/07/the-mail-you-want-not-...
[0] http://gmailblog.blogspot.com/2015/07/the-mail-you-want-not-...
I'm not against Gmail, just like I'm not against Outlook.com or Yahoo mail or something. It's just that providing tools only work for players in a power position (i.e. Google) who can afford to ignore small players (i.e. me), and what's more, this further strengthens their power position: the better they can detect spam so more people will start using it (the postmaster tools are there to help people prove they are good, thus helping Gmail distinguish).