I think it's just Google having a strange idea of suspicious.
For example, I have 2 Google accounts that are both intrinsically linked. I wanted to get a URL link from my computer into my phone quickly so I emailed it from one Google account to the other in the web app.
Sure enough, it plopped straight into the spam folder! To make matters worse, when I went in to look for it I found about 50 google+ notifications!!
If Google thinks traffic generated by the Google product roster is suspect, then nothing else has any chance!
Was good that i found I had comments on videos though. I thought nobody loved me any more!!