Going through the xfinity site through Firefox.
When I click on the email to open it, then read it, and it is not showing as read. I have to click on the envelope again to mark it as read. I would think the default would be to automatically mark it read but it doesn't. This just started about a week or so, apparently when an update was made to the email. Thanks for responding.
Try clearing out Firefox's cache/browsing history. When you have done that, close it out and re-start it in a fresh session. If that doesn't do it, then try using a different browser.
Click on the link below. When you get onto the Mozilla site scroll down to "How do I clear my history?" You will want to select "Everything".