Today I noticed a strange warning when opening a mailbox:
WARNING: The object domain.local/Productie/Users/SomeOU/LoaderA0001 has been corrupted, and it's in an inconsistent state. The following validation errors happened: WARNING: Property expression "LoaderA0001" isn't valid. Valid values are: Strings that includes '@', where '@' cannot be the last character
It complains about the @ sign being an invalid character, but it’s not in there!
I opened PowerShell and used the Validate method off the Mailbox object and this gave a more precise error:
Constraint : Microsoft.Exchange.Data.RegexConstraint InvalidData : LoaderA0001 PropertyDefinition : UserPrincipalName (System.String) Description : Property expression "LoaderA0001" isn't valid. Valid values are: Strings that includes '@', where '@' cannot be the last character PropertyName : UserPrincipalName
So it appeared to be a problem with the userPrincipalName attribute, I first changed it through the Exchange Management Shell but I got the same error there.
Then I opened the object with ADSI Edit and cleared the value of userPrincipalName:
Then I set the correct value using the Exchange Management Shell and that made everybody happy again!