Deliverability of email distribution to Comcast emails

Hi there- I've done some extensive searching (including on this forum), and it looks like there's some frustration regarding certain spam filtering and the time it can take to "train" the spam filter for certain wanted (or un-wanted) messages. 

This being said, I send an email distribution to about 2000 comcast emails per day and all of these emails are actively engaged (open at least a couple times a week). Last week it became apparent that all of these emails started going to their spam. Open rates dropped almost to zero and multiple folks were reaching out asking where it had gone. I was hoping to get some guidance from Comcast on the issue. Thanks for your help!