email flagged as spam

We are having tons of email flagged as spam in both directions with our Comcast Microsoft 365 email.  It is causing huge issues.  We have gone through every setting we can think of.  When I email the Comcast support address provided, it gets bounced back and is not delivered.  I have tried calling support but just got someone that referred me to google.  Is there any way to have someone at comcast look at our email settings and fix them?  We are at our wits end.