Exchange Autodiscover Authentication fails after mailbox migration from 2010 to 2013 is completed; until server is backed up or rebooted

Solution 1:

UPDATE: There is now fix for this. The workaround is to set the autodiscover application pool to recycle every 30 minutes, and do your user migrations to Exchange 2013 to off working hours.

Im having almost the same issue. Im still trying to find out what is causing it, but you don't need to do a complete restart of the server, you can just restart the autodiscover pool in IIS on the frontend server (in my case the CAS and MBX role are on the same server).

The issue seems to be that the Ex2013 FrontEnd server (where the user was connected while he was migrated to Ex2013) still proxies the request to the Ex2010 servers event though the user is migrated. Im still no sure what is the cause, and how to fix it. If I find a solution to the root cause I'll let you know.

Solution 2:

This issue occurs because the cache on the server didn't get update. Generally, recycle the Autodiscover application pool on Exchange 2013 server would be enough:

Restart-WebAppPool MSExchangeAutodiscoverAppPool

Here is the Microsoft KB: https://support.microsoft.com/en-hk/help/3097392/outlook-logon-fails-after-mailbox-moves-from-exchange-2010-to-exchange-2013-or-exchange-2016