Comcast preventing emails from being delivered

I've been having a problem with numerous emails sent to me not being delivered.  For example, I receive daily newsletters from a newspaper I subscribe to.   When I used a non comcast email account as my contact info,  I had no problem.  But since switching to comcast as my main contact, some never come at all and others do for a while, then just stop.  Another example would be the best buy deal of the day email.  I'm signed up for it, it came for a few months, then just stopped.  Given the number of senders this happens with, it is a comcast issue--the chances of it being a sender issue and it all happening around the same time is one in a trillion.  Calling tech support gets me nowhere.

It shouldn't have anything to do with settings on my computer or mobile device b/c those haven't changed (whatever settings I had before the problem I still have).  Nor should it have to do with settings on my sender accounts b/c those haven't changed either.