Some. but not all, of the time, I cannot receive emails from a particular user, whose emails are not going to a spam folder or otherwise being reported as "junk."
Check your Spam settings. Make sure that "Enable spam filtering" and "Save a copy of emails marked as spam" are both selected (see https://www.xfinity.com/support/articles/spam-filters-and-email-blocking-new-experience).
If the settings are correct and @ComcastAntiSpam or another employee doesn't reply to your message here, Comcast Security Assurance should be able to help. You can reach them at 1-888-565-4329 (from https://internetsecurity.xfinity.com/help/report-abuse/). Note that this is NOT one of the general customer service numbers.
The first-line reps there are sometimes not very helpful, so you may need to be persistent and keep at them until you get a satisfactory answer.
@melissa-mcclell Could you provide any details, such as the domain of the sender?