Email going to spam even though the address is in my address book

@user_e0hewt 

I am accessing my email through a new Edge browser.  In the last month, emails coming from one particular address are going to my spam every time they come in. 

I have made sure the address is in my address book.

How can I get this fixed?  Is this a problem on the sender's side?

Mark the email as Not Spam.  You may have to do it a lot before Xfinity gets the idea, though.