Cannot Receive Legitimate Emails from Clients but can Receive Junk Mail

I have had Comcast Busines email for about 3 years now.  In the last three days I have noticed that I am not getting any legitmate emails from my contacts/clients, but I can send out emails.  The strange thing is that I can receive Junk emails (about 10-20 per day, typically 30 mins apart, all with the .us domain extension).  I access my e-mail typically using Outlook 2016, and I have checked my mail through OWA and my phone and all my inbox shows is these junk emails.  Sometimes they migrate over to my junk email folder and sometimes they don't.   I have spoken to clients and they have not received "undeliverable" notices.  I have also sent emails from other accounts with the same results.  The emails to my comcast business account just disappear.  I have a tier 2 ticket open but have heard nothing for 3 days.  So, I am about ready to pull the plug on Comcast.  Any help would be appreciated.