Attempting to set up an exim4 SMTP only server that can send out messages from two domains
Adding this line to the the config file (update-exim4.conf.conf)
PRIMARY_HOSTNAME = $sender_address_domain
Gave the follow header:
Received: from [...] (helo=name)
By MAIN_HARDCODE_$sender_address_domain with esmtp (Exim 4.96) (envelope-from [email protected])