Set-Mailbox fails, update "Send on behalf" exchange 2010, recipient isn't the expected type.
When update "sent on behalf", you may face error "recipient isn't the expected type"
"Send On Behalf" access has not been removed while disabling the mailbox, they accounts are still pointing to shared mailbox, it usually happens with migrated exchange.
Go to AD Users & Groups
Select email account having problem
Click properties and select Attribute Editor
select PUBLIC DELEGATES and remove the mailbox account you seen in the error.