Exchange 2013 / Outlook issue - Slow even on OWA for single user

[RabbieBurns]

We have recently migrated from exchange 2010 standalone server to an exchange 2013 cluster.

 

Previously we had a single DB, Single server. Now we have 4 servers, 3 databases.

 

Everything is working pretty well, except for one user, whose mailbox is causing him all sorts of grief.

 

Using any mail client (OWA, iOS Mail, Outlook for iOS, Outlook on Mac) the performance is completely unusable. Switching between mail and calendar takes upwards of 60s. There are duplicate calendar entries appearing and reappearing. This *seems* to have started since he installed the beta of Office 2016 for Mac, but there a whole bunch of us in the office using this same version with no problems.

 

I have tried multiple troubleshooting steps but cannot figure this one out, so hopefully someone here can think of something I haven't.

 

• Removing the mail from all mobile devices
  
• Running a New-MailboxRepairRequest (nothing found)
  
• Moving his mailbox from one db to another to remove any corruption (there was 0 'bad items')
  

 

This is causing the user a massive loss in productivity, and it happens to be my BOSS!

 

So, is there anything else I should think of. Perhaps getting him to uninstall office 2016?