Problem with autodiscover after migrating mailbox to O365

[CyBeRkId2002]

Morning all,

 

I am currently experimenting with Exchange Online in Hybrid mode with a view to migrating our students to the cloud over the next few weeks. Everything seems to be going well, got them connected, test accounts migrated etc. but we are stuggling with getting autodiscover to work after the move.

 

I have run the Exchange Remote Connectivity Analyser and found that:

 

• Auto discover is correctly getting to our internal mail server
  
• The request is correctly getting redirected to Microsoft
  
• The Microsoft tests are failing on HTTPS (as I believe they should) but succeeding to connect on HTTP
  
• It gets to the final step but fails at "Autodiscover settings weren't obtained when the Autodiscover POST request was sent."
  
• The autodiscover request is for @brockingtoncollege.mail.onmicrosoft.com NOT @brockington.leics.sch.uk
  

 

The above leads me to believe that it is looking for a user with a User Principal Name that does not exist (the error spells this out). My question is how to fix. Should the primary UPN on Exchange Online be the .mail.onmicrosoft.com address (would be very surprised if so) and if not what do I need to change locally to get it to correctly pass on the @brockington.leics.sch.uk request.

 

Any guidance would be much appreciated!

[CyBeRkId2002]

Would anyone who is currently running hybrid mind going here https://testconnectivity.microsoft.com/ and running the Outlook autodiscover test. Particularly interested in whether the second request (the redirect) leaves the email address as @Yourdomain.sch.uk or changes it to the onmicrosoft one.