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Outlook Client Does Not Connect to Mailbox on Exchange 2016

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Resolve Outlook connectivity issues after moving mailbox to new Exchange 2016 server
Lately, it seems as if I run across some new issue or anomaly on a weekly basis after implementing Exchange 2016 for one customer or another. It's quite frustrating but it does wonders for building a personal knowledge base.
One of the latest issues I've experienced has been with an Outlook client (2010 or newer) not connecting to a mailbox that has been moved to (or even newly created in) Exchange 2016.
What's odd to me is that this experience is inconsistent with other mailboxes that were previously moved to Exchange 2016 and Outlook is connecting without issue.
Essentially what happens after an existing mailbox has been moved to Exchange 2016 and the Outlook client is restarted, the auto configuration process fails during the "Log on to server" task.
As a result, Outlook is never able to attach to the mailbox on Exchange 2016 or update the existing profile. And, unfortunately, during the Outlook profile reconfiguration, the option to run the Outlook connection status and auto configuration tests are unavailable to see what the issue might be from the workstation.
Autodiscover is confirmed to be configured properly and works fine; and tests using http://exrca.com work without error.
Again, other users are able to connect to their Exchange 2016 mailboxes. Also, the users are able to connect to their Exchange 2016 mailbox using OWA and smart devices.
And when the mailbox is moved back to the legacy Exchange server, Outlook connects without issue. Also, the issue exists on other workstations and varying Outlook clients while attempting to connect to the same mailbox.
Efforts to resolve the issue that were unsuccessful, included...
  • Delete the Outlook profile and recreate.
  • Export the mailbox contents to PST, delete the mailbox, and create a new one on legacy server and move to Exchange 2016.
  • Export the mailbox contents to PST, delete the mailbox, and create a new one on Exchange 2016.
  • Delete the Windows profile.
Unfortunately, the only resolution we stumbled across was to delete the Active Directory user account and associated mailbox, and then create brand new items for both. This is not an ideal resolution by any stretch of the imagination.
In my frustration, I posted a question to the community in hopes for a quick response; and I got one.
The suggestion was based on a Microsoft KB article ... Outlook logon fails after mailbox moves from Exchange 2010 to Exchange 2013 or Exchange 2016.
Essentially, the resolution suggested is to restart the Autodiscover App Pool on the Exchange 2016 server where the "problem" mailbox resides. Simple enough, right?
Restart-WebAppPool MSExchangeAutodiscoverAppPool

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Well, it was just that simple. We restarted the Autodiscover App Pool and the other handful of users experiencing the same issue where able to successfully close (and reopen) Outlook to complete the auto reconfiguration of their profiles after their mailboxes were (or had been) moved to Exchange 2016.
Even though Autodiscover was configured properly, I suppose the ability for Exchange Managed Availability to self-heal the offending app pool in Exchange 2016 server didn't resolve the issue as I might have assumed it would. But, I also suppose a restart of the server might have addressed the issue as well.
Good luck and have fun!

Author:Todd Nelson

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