I have a customer that is having an issue with Outlook 2013, emails randomly get stuck in the Outbox and won't send. I have looked at this issue and the emails do not have any recognizable pattern. The emails are addressed to different email addresses, with and without attachments, internal and external emails. The issue is not consistent, it pops up every day or so but cannot be reproduced other than when it decides to appear. When the issue appears the emails cannot be opened or manipulated or Outlook will crash. Upon starting Outlook again the emails are gone from the Outbox but not in Sent Items.
This customer has Exchange with many more users that are not having any problems. The customer let me know that the only two people who are having this issue have Windows 8.1 and Outlook 2013. These are the only two users in the company that have Windows 8.1. Users on Windows 8 and Windows 7 do not have this issue.
I have seen many internet posts that hint that this issue is related to Windows 8.1 having a flaw but I have not found anything conclusive. I have held off on performing all of the tradition Outlook troubleshooting tasks so that I don't disrupt the user if the issue is truly related to a Windows update or bug.
Please let me know if you have any suggestions.