I have setup several devices on our internal network to use our internal Exchange Server to relay emails and it works fine. I ran into something last night when I added a new all-in-one printer that has scan to email. This department has a different domain for their emails than is configured on our internal domain. I do not host their Exchange Server. I would still like to be able to forward their emails for them.
Example our domain is mydomain.com and their domain is theirdomain.com.
When the sender email address is configured as firstname.lastname@example.org the emails do not relay off of our Exchange Server.
How can I configure the Exchange Server so I can have them have theirdomain.com as their domain for emails?
Just to clarify they are users on our internal domain but their email domain is different than our internal domain and a third party hosts their email server for them.