Ok, I understand the Send on Behalf of functionality, but what I"m looking for is a little different.
I've got user abc who is setup in my active directory. In my exchange setup, user abc has multiple SMTP address: firstname.lastname@example.org (this is set to the primary) and email@example.com.
I want this user to have the option of sending mail and having it appear as it is from firstname.lastname@example.org. Currently, it defaults to the primary address. I can change the reply-to address, but the from information still appears to be email@example.com. If I try and change the from address, active directory resolves the firstname.lastname@example.org address that I've entered in and changes it to email@example.com.
Any way around this? Or will I need to create an additional AD account?