In Exchange 2010/2016, you might come across a strange error as shown below when sending email:
Failed to process message due to a permanent exception with message Invalid named property
To fix this problem, you need to move the mailbox to another store with a specific switch:
- New-MoveRequest “User” -DoNotPreserveMailboxSignature -TargetDatabase Store1
Once the move has completed, you should no longer receive the delivery error above.
Hope it helps.