I was running an Immunity Challenge on my site and got 7.000 people signing up within a week. We had pretty soon delivery issues with messages going into SPAM on Gmail, and things were better after reducing the speed of sending emails. After a few days we had increasing problems with Hotmail which seems to be notorious for sending messages to SPAM.
I started to mail out on a weekly basis to my list, and after 3 months I suddenly have increasingly problems with Gmail again. Testing with https://www.gmass.co/ I see that the majority of messages goes to SPAM, which did not happen 3 weeks ago. Sending from a different Email address that has a list of 1200 subscribers, I have no SPAM problems at all. When I use https://www.mail-tester.com/ it tells me that the SpamAssasin score is bad, especially in relation to Razor:
Razor2 gives confidence level above 50% cf: 100
Listed in Razor2 (http://razor.sf.net/)
I am kind of stunned and wonder what I can do about that problem. I have proper setup of SPF, DKIM and DMARC and using Amazon SES for sending. All properly set up. Any hint what I could do will be welcome.