MS Outlook 2013 showing an nonexistent unread email

Question

I'm facing a problem with my Outlook 2013. In the 'Inbox' folder, there's a number indicating an unread e-mail. I've entered into all folders of my account (including search folders, MS Lync conversation folders, and RSS feeds), and it doesn't exist.

I've tried outlook.exe /cleanviews but it didn't worked.

Answer 1

Well, some time later, i just discovered what's going wrong.

I needed to go to my webmail (mail.office365.com), log-in and then there was an unread email. Marked it as read, and Outlook didn't showed it anymore.