spam filtering legitimate emails

My personal Comcast email address will not accept legitimate emails into my inbox.  All emails go to spam folder.  Despite my having indicated that they are "not spam".  Also despite my adding the specific sender address to address book.  Nothing fixes this except completely turning off spam filtering.  The problem is with all emails from any sender at a particular .gov entity.  It also happens with every Comcast address that any of those .gov senders email to.  Clearly a Comcast problem, not recognizing the legitimacy of the sender.  I have spent hours trying to get answers from Comcast.  Twice I finally got through to a live agent who promised to escalate the problem to a "back end" team and that I would very soon get a call back.  Never happened, twice.  But I did get follow-up questionnaires about my service experience (one in Spanish, with no reason)!  Despite describing the experience as awful, I still get no help. Any suggestions?  In the meantime, I am considering having my Town change internet provider from Comcast, when the contract is up for renewal.  Thanks.