Same problem here. Happening to 3 out of about 60 users, all on EEA 5.0.2214, all Windows 7 64bit. 2 have Outlook 2010, 1 has Outlook 2013. Connected to Office 365 for Exchange.
See attached image. 'Invoices' is the user mailbox, the blacked out From is the sender. Looks just like a draft, but it's an incoming message.