Personal Comcast email going to junk

Since Friday, when I send an email to anyone from my Comcast account it is being either totally blocked (not received) or sent to person's junk folder.  For example when I send myself an email it goes to my junk folder.  When I send other Comcast friends emails, it goes to their junk folder even if I am listed as a contact.  When I send to some people's work email addresses, it doesn't even get there so I assume it is blocked by their servers.  I've spent over 2h on phone with Comcast and no one has been able to help.  It appears my email address somehow got on some blocked list somewhere or the settings somewhere got changed.  Advice PLEASE.