I have Office 2013 on Windows 7 and have noticed the following behavior in Outlook:
- New mail arrives in my Inbox
- Envelope icon appears on the Outlook icon in the taskbar
I now read the email on another device
- The email is automatically marked as read on the first machine
- The envelope icon persists in the taskbar
The only way to get rid of the icon is to either toggle a mail from read to unread and back to read or if I get another email and read it on the machine that has the icon
This behavior causes a lot of false positives when reading emails on two machines.
Note: I raised this issue on the MS community forums and they were able to reproduce it. I have added the link below. I am posting it here based on feedback I received there.
http://answers.microsoft.com/en-us/office/forum/office_2013_release-outlook/new-mail-notification-envelope-icon-does-not-go/8c3a9e25-e7d3-4bb2-9a07-f2481f5feb46