Still the same problem. If I read an email on my phone thru the app and don't delete it before checking email on my pc the email gets stuck in the iPhone app. Only fixable by deleting the app and reinstalling. Fix??? This has been a problem since my iPhone 4!!!
I had the same exact issue when I had my 3GS phone and just thougt it was the phone. I now have the iPhone5 and the issue still exists. Hopefully someone can address this. I would rather use the Xfinity App and not the Mail app that came with the phone.