have a user with rights to send on behalf of another mailbox. If the user logs in to another computer, and sends an email from another mailbox with delegate rights, the email is sent with on behalf of rights. But, when the user uses his own pc, the email is sent only as.
It would appear to me is not a problem with server, because it works from another computer. Did a repair of Office 2010. Still same issue. Not sure if anyone has any other ideas?