Are you seeing this in Comcast webmail or some other web page, program, or app? If webmail, what is the address of the page? "web.mail.comcast.net/zimbra/..."? "connect.xfinity.com/appsuite/..."? Something else?
I'm a different user with the same problem. This started with the email "upgrade" that happened two days ago. I got it corrected yesterday but this morning it's flipped back and nothing I've done has worked.
Email on my iPad has the same issue, haven't tried to change that
@OlLadyMcKnight wrote: Connect.xfinity.com/appsuite ...
The old "Zimbra" email had an option to turn this on, but I don't know of one in "Appsuite". I'm showing Version: 7.8.4-6-107 (gear icon / About). Are you showing a different version?