When you try to brows user mailbox using owa you get this error :
Issue
The error message is:
InnerException: Microsoft.Mapi.MapiExceptionADPropertyError
Solution
This error come from wrong Value of legacyExchangeDN attribut , you should delete the wrong value and put a good one for Example : /o=OrgName/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=UserAlias.
SHMUEL H.