Hi,
We have an Exchange 2010 Server with multiple Users sharing a mailbox
This mailbox is used to send bulk emails out to clients. The emails are prepared in a third party application, and dumped into the Outbox of the open mailbox in Outlook. The users have the mailbox added on a separate profile in Outlook.
When processing the bulk send, the mails arrive in the Outbox, however, they are returned from Exchange with the following message:
Delivery has failed to these recipients or groups:
You can't send a message on behalf of this user unless you have permission to do so. Please make sure you're sending on behalf of the correct sender, or request the necessary permission. If the problem continues, please contact your helpdesk.
In so far as we are aware no changes have taken place on Exchange aside from the contacts list on exchange and address books.
We have managed to temporarily resolve the problem by removing the Offline Address Book and allowing it to resync with Exchange.