We purchased a company that utilizes POP3 to access hosted email. Since we use MS Forefront Protection in the public cloud to filter our incoming mail, I will add the purchased company's domain to our MS Forefront Protection and change their MX record to point to it. My question has to do with adding the purchased domain to my Exchange server. The president of our company wants all employees of the purchased company to keep their old email addresses along with a new address in our domain. Also, he wants all email sent by these new employees to go out with the purchased company's domain address. For example, these users will have the following two addresses: firstname.lastname@example.org and email@example.com. All of their email messages should have a reply address of the purchased company. Can I add the purchased domain to my Exchange server; add alias addresses for the purchased domain to their already created mailboxes in our domain; then set the alias as the reply address. Will this work?