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You are migrating the mailboxes from Exchange 2010 to Exchange 2013 or Exchange 2016. You can face the issue that users with Outlook are not connecting to the Exchange Server. There should be an explanation for this issue and why this is happening in the first place.
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Outlook not connecting to Exchange
What is happening? The user mailbox migration completed. The migration of the mailbox was from Exchange Server 2010 to Exchange Server 2013 or Exchange Server 2016. The user starts up Outlook to connect to Exchange Server. After restarting Outlook, the client remains disconnected.
Why is it happening?
After the mailbox move completed to Exchange Server 2013 or Exchange 2016. It continues to proxy the autodiscover request to Exchange Server 2010. Exchange Server 2010 responds with a 302 redirect back to Exchange Server 2013 or Exchange 2016.
What is the fix for Outlook not connecting to Exchange?
To resolve this issue, restart the MS Exchange Autodiscover Application Pool.
Restart the Autodiscover Application Pool on the Exchange Server 2013 or Exchange Server 2016 servers. There will be no disruption when the MSExchangeAutodiscoverAppPool is restarting. Note: do this on all the Exchange 2013 or Exchange 2016 servers!
Run PowerShell as administrator and run the following command.
PS C:\> Restart-WebAppPool MSExchangeAutodiscoverAppPool
Restart Outlook client and they should be able to connect to the Exchange server.
What if you are going to migrate a lot of users in the coming weeks?
You need to restart the Autodiscover Application Pool every time the migration finish. Doing this the manual way is not the best practice. You are busy with other tasks and can’t keep an eye all the time to run the command when a mailbox finish. What if you do the migration at night and the users start early in the morning? You can wake up very early and restart the MSExchangeAutodiscoverAppPool. I guess you love to have your sleep, don’t you?
Solution: Automate the restart of the MS Exchange Autodiscover Application Pool.
Automate the fix
Open Internet Information Services (IIS) Manager on your Exchange Server. This can be your Exchange Servers 2013 or Exchange Servers 2016.
Select 1. Application Pools, select 2. MSExchangeAutodiscoverAppPool and select 3. Basic Settings.
Enable Regular time interval (in minutes) and set 5. Click on Next.
Select all checkboxes and select Finish.
The MS Exchange Autodiscover Application Pool will restart every 5 minutes.
In this article, you learned why Outlook is not connecting to Exchange after migration. After understanding why it is happening, you can apply the fix. Recommend is the automated way. Did you enjoy this article? You may also like Migrate Exchange mailboxes through text file. Don’t forget to share and follow us.