Can't receive emails from our school district

I'm reaching through my personal account since I can't from my work google hosted account (public school district).  If anyone of us email a comcast.net account we get "The response from the remote server was: 530 5.1.0 sender rejected".  I tried the https://spa.xfinity.com/report but I don't think it's an IP issue since we are hosted and I don't see our domain on any RBL list.  What is the best way to get this resolved?  This started on Sept 29 around 11:00am EST.