Extremely long delays---many HOURS-- to receive incoming email to my Xfinity address

My incoming emails are regularly being delayed by up to several hours. This is a VERY bad situation:( I'm elderly and often need to reach my children. PLEASE let me know how this can be fixed. My son who is very technical and is submitting this request, has saved the appropriate header/source information to help you track down this issue. My son has confirmed with 100% certainty that my highly delayed emails have in fact been sent--they are NOT sitting in outboxes. Please let us know with whom we can share a sample email source info so you can diagnose and solve this issue. Thank you very much.

[Edited: "Personal Information"], longtime Xfinity customer 

and her son, [Edited: "Personal Information"], who is his mother's IT assistant:)