Hello,
An email from another company addressed only to one person, that being a single recipient in our company, disappeared from the users iPhone (6s running 9.3.5) shortly after seeing it listed in the Mail app and I later discovered that it was in the Outlook Web Access (Exchange 2010 14.3.123.4 on 20088R2 Standard) outbox for that user/recipient. The user never viewed it in Outlook or saw it in the Inbox. I found a copy of it in his Outbox in OWA by doing a search for the email, but did not find it in Outlook’s outbox. He hadn't accessed OWA.
What might explain the presence of the email in the OWA outbox?
-I’ve since unenrolled/reenrolled the iPhone in AirWatch as a precaution.
-I've removed 4 extra/old devices from ActiveSync for the user so that only his current two devices are shown.
-There were no rules in Outlook or OWA for the user that could cause this that I saw.
-I found nothing unusual in how the email was received through Mimecast (auto allow) or Exchange (Receive and Deliver EventID's in Message Tracking).