After Update All Email Marked "unread"

After updating to iOS 7, my email icon says I have 4,000 unread emails! I open the app, select all, and tap "Mark As Read," but they all remain unread. I am a Comcast customer and I also have the Xfinity App which is working OK. Search of keywords seem to indicate the problem has to do with it being a POP3 account. Don't know what that means or how to fix. I deleted the account from the phone for now and I only use the Xfinity app to read my mail. Will re-enter my account as soon as I find a way for it to work correctly. Thanks for any suggestions!

via iLounge Forums http://forums.ilounge.com/iphone/278423-after-update-all-email-marked-unread.html