Prevent email from going to SPAM

Hi.  Email from a specific sender keeps going into my Spam folder, even though I do not consider it as such. Everytime I catch such email in the Spam folder, I mark it as "Not spam".  I also added the address to my webmail Address Book, per https://forums.xfinity.com/conversations/email/how-to-prevent-email-from-going-to-the-spam-folder/602dafffc5375f08cd1ec7b9.  But I continue to get mail from that address deposited into my Spam folder.  Are there any other suggestions for how to disuade the Xfinity Spam filter from trapping email from this sender?

Note that I have Xfinity's "Spam Filtering" enabled in "Advanced Settings". I do not wish to disable it and manage such filtering on my own with a bunch of Filter Rules.  Nor do I wish to enable "Email Safe List" functionality.  Both of these alternatives require much more maintenance activity on my part than I care to pursue.  If those are my only other alternatives, I will live with the current annoyance. 

Thanks.