Successfully configured SBS2011 with secondary domain. Incoming mail is received.
Where user has been configured within a given company and the priorities have been configured for that company then they can both send and receive from the secondary domain.
Where the user needs to retain the primary address, but occasionally send emails from the secondary address then I select the secondary email from the [FROM] option in Outlook. The email address here is the one that the user has just received from successfully.
The result is a "Delivery has failed to these recipients or groups:" failed message with the following in the body:
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.
I need to send as either email account and need to attach the appropriate signature when doing so. The alternate email is not a separate mailbox or user, but simply an alias - given that the email address cannot be picked up amongst the mailboxes, even though it can be used successfully by those users who have had it configured as their primary address and all incoming mails find their targets successfully.