If you just finish Tenant to Tenant mailbox migration, you probably will run into issues with outlook reconfiguring the mailbox in outlook.  Here are some a few solutions that will help in fixing the problem. Basically, the idea is to delete the previous login and outlook identities so that you can add  the email again in outlook.

Solution 1 – Clear all outlook identities in windows registry .

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\x.0\Common\Identity\Identities\

Delete identities.

Solution 2 – Configure subkey in the registry

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Autodiscover
DWORD: ExcludeLastKnownGoodUrl
Value: 1

Solution 3 – Clear all credentials

1. Click the START button and type CREDENTIAL MANAGER then click on it
2. Click the WINDOWS CREDENTIALS TAB
3. Expand every item one by one and select REMOVE

Solution 4 – Delete License data

%localappdata%\Microsoft\Office\16.0\Licensing\

Solution 5 – Override ADAL WAM

Run the following command in command prompt

REG ADD HKCU\Software\Microsoft\Office\16.0\Common\Identity /v EnableADAL /t REG_DWORD /d 00000000 /f
REG ADD HKCU\Software\Microsoft\Office\16.0\Common\Identity /v DisableADALatopWAMOverride /t REG_DWORD /d 00000001 /f