Hello,
I have been using MIAB since quite a time now, and I am still having issues with Gmail and their way of detecting spam. I could say that 90% of the emails I sent to Gmail accounts are marked as spam. And believe when I say it is not spam.
I have a 10/10 http://www.mail-tester.com and all similar services I could find. What else could I do to ensure Gmail does not set my emails as spam?