Not receiving all emails

For the last 6 months, I am not receiving all emails from non-comcast addresses (including billing statements/payments, personal yahoo, Amazon, health insurance).  It doesn't matter if I am accessing through the Xfinity Connect App, Xfinity website or Windows Live Mail  -- same emails show/same emails don't.  This seems to be a huge issue in the forum, with minimal assistance.  I have looked online and many computer service assistance sites/videos point it toward a Spam filter that is managed by Xfinity and not something customers see (even spam folders don't show missing emails).  I have checked settings, no filters, no forwarding, no rules...  PLEASE HELP!!