Only when using outlook.com site, Inbox shows 1 unread email message where none exists that I am aware of.  Using Win 8.1 Pro on 3 different PC's.  Neither latest Mail app nor desktop version of Outlook 2013 show any unread emails on any of the 3 different PC's though outlook.com displays same 1 1 unread email on all. 

Have attempted multiple times on outlook.com, first selected "all" emails in my Inbox and marked "unread before read" with no affect.  All other functions appear normal.  Suspect it is an issue at the outlook.com site.  Suggestions or ideas?