Email Message Blocking

I've received 3 "Non-Delivery Report" messages today when responding to previously received messages stating "Your message was believed to contain questionable content and therefore was not delivered to the intended recipients. The information above will help Xfinity with any questions you may have."

I have just spent over half an hour on the phone with an Xfinity customer service agent who keeps telling me that new Xfinity software is scanning emails for "suspicious" content & must have contained something "questionable." I am currently on hold after requesting this issue be escalated for an explanation as to what content in my message was deemed "questionable" by whatever algorithm is being used.