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.

By edward