Email screen problem

My email screen has a train of 1" black boxes at the bottom above the dock frpm side to side. Each box says  M...    I would appreciate any thoughts,  I am using iMAC Catalina 10.15.5

I recently had a problem finding the 'save' function when making a draft as its now buried under "discard" of all places, so some changes have been made to Xfinity email.  Support from India wasn't of any help.