Emails not being displayed in correct order

Hi,

 I've a user who's emails aren't showing in the correct order, 

As you can see in the image, the sort order of the emails is being displayed incorrectly - not in chronological order.

We have carried out the following:

Amended the Arrange By properties, removed + re-added the account to Outlook For Mac.

Outlook version is 15.8.2  which is the latest stable release within our organisation.  Connected to Exhange 2013 / O365 account.

Isolated to one user. 

Issue still occurs with both Unread and Read emails. 

Issue does not occur when using Outlook on Windows machine or when using Mail app on iOS device. 

OS version is Yosemite. 

User can send / receive emails successfully. 

Any help would be most appreciated. 

Thanks.

Alastair