I have a user with constant outlook issues. ie freezing and messages getting stuck in the outbox.

We don't use roaming profiles, and this is the case on several freshly built devices.

I've created a new mailbox - which hasn't made a difference so I'm thinking it could be an issue with the user account.

What would be the best way to troubleshoot this? Or replace the user account?

Hi,

From your description, I recommend you check if OWA works well. If yes, the issue is related to Outlook side, please follow the steps below for troubleshooting:

1. Please check if your mail server is offline.

2. verify if it is a wrong or changed password.

For more information, here is a kb for your reference.

Email stuck in the Outbox in Outlook 2010 / 2013

http://social.technet.microsoft.com/Forums/en-US/4f9f0630-9527-455d-a2d0-5ae682536c00/problem-user?forum=exchangesvrgeneral

If the issue persists, please use Outlook safe mode to determine whether the problem is caused by add-ins.

Hope it helps.

Best regards,

Try OWA to see whether that is fine for the user.

Clear any rules, start outlook in safe mode etc can also be attempted. From the run tab, execute outlook.exe /safe