If you're hosting your email with Microsoft's Office 365 service, you may be using shared mailboxes. You should if you aren't, they're a great way to create email addresses that don't consume a license.
I've done a few dozen installs of the new office 2013 on various machines lately and until now all email hosting has been through either gmail or 0ffice365 so I hadn't come across the issue of messages being stuck in the outbox. In my case the email account in question was an IMAP account and no matter what I did...
