Symptoms
When mailboxes are moved to Exchange Server 2013 or Exchange Server 2016, users can no longer access those mailboxes.
This issue occurs in the following scenario:-
A user typically uses Outlook Anywhere to connect to his or her Exchange Server 2010 mailbox.
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The user's mailbox is moved to Exchange Server 2013 or Exchange Server 2016.
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After the mailbox is moved and the user tries to log on, he or she is prompted that “The Microsoft Exchange administrator has made a change that requires you quit and restart Outlook.”
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After Outlook is restarted, the client remains disconnected for up to 12 hours.
Cause
After the mailbox move is completed, Exchange Server 2013 or 2016 continues to proxy the autodiscover request to Exchange Server 2010. Exchange Server 2010 responds with a 302 redirect back to Exchange Server 2013 or 2016 (depending on the upgrade).
Resolution
To resolve this issue, restart the Autodiscover Application Pool on the Exchange Server 2013 or Exchange Server 2016 servers.
Restart-WebAppPool MSExchangeAutodiscoverAppPool
More Information
In this scenario, the HTTPProxy\Autodiscover logs contain information that resembles the following:
2015-06-16T16:01:23.845Z,d511bfef-a7e0-4e7d-beb8-6e6f8c0d2bd9,15,0,1044,21,,Autodiscover,autodiscover.fabrikam.de,
/autodiscover/pmcu9..fabrikam.de/autodiscover.xml,,Negotiate,true,FABRIKAM\pmcu9,fabrikam.de, Smtp~pmcu9@fabrikam.de,Microsoft Office/15.0 (Windows NT 6.2; Microsoft Outlook 15.0.4569; Pro),192.168.2.115, E15SRV1,302,302,,POST,Proxy,e14.fabrikam.local,14.03.0123.000,IntraForest,ExplicitLogon-SMTP,,,,349,201,1,,3,1,,0, ,0,,0,0,,0,24,0,1,0,0,16,0,0,0,0,0,21,0,17,4,4,7,24,,,,BeginRequest=2015-06-16T16:01:23.829Z; CorrelationID=<empty>;ProxyState-Run=None;DownLevelTargetHash=0/1/2;ClientAccessServer=E14.fabrikam.local; ResolveCasLatency=0;FEAuth=BEVersion-1937997947;ProxyToDownLevel=True;BeginGetRequestStream=2015-06-16T16:01:23.829Z; OnRequestStreamReady=2015-06-16T16:01:23.829Z;BeginGetResponse=2015-06-16T16:01:23.829Z; OnResponseReady=2015-06-16T16:01:23.845Z;EndGetResponse=2015-06-16T16:01:23.845Z; ProxyState-Complete=ProxyResponseData;EndRequest=2015-06-16T16:01:23.845Z;,