Not receiving emails from some senders

A couple of years ago, Comcast seemed to block all of the emails I was receiving from my Nextdoor neighborhood group.  The Nextdoor emails were not showing up in Spam, they just stopped coming abruptly when before that they had been coming regularly.  I tried resubscribing and it worked for a short time, but then the same thing happened again.  I gave up and just ask my neighbors what is going on. It has happened to my NYTimes digest emails so I log in to my NYTimes account to read the news.

Now, all emails from Paperless Post have stopped.  I have gotten Paperless Post to help me resubscribe a couple of times, but it is still a problem.  PP customer service reps said that the reason it continued to happen was that I was marking PP emails as Spam.  I do not mark PP emails as spam, and the first time it happened I added the PP email addresses to my Comcast address book. This week, when I asked for PP help to resubscribe, I was sending out a Paperless Post to an event where I am a host but also on the list as a guest.  Because I had just worked with the PP customer service to resubscribe, I expected to receive the invitation just like all of the other guests.  Instead, as soon as the invitation went out, my account popped up as 'Unsubscribed' so it must have been filtered by Comcast as Spam before it got to anything that I could control.  

This experience with Paperless Post is particularly frustrating because I do not have a work-around the way I can login to the NYTimes.  It also happened with a knitting group I really like to follow (Modern Daily Knitting) but I resubscribed to their newsletter using my gmail account. I believe it has happened to other newsletter type emails as well, so when I care about something now I just choose gmail, but I would love to be able to count on my Comcast emails as well.