7.18. Accepting Mail for Multiple Domains
Problem
You want the recipients in your Exchange organization to be able to accept mail for an additional domain without having to configure separate secondary addresses for each recipient.
Solution
Using a graphical user interface
Open the Exchange System Manager (Exchange System Manager.msc).
Expand the organization→ Recipients→ Recipient Policies.
Right-click the desired policy and select Properties.
Click the E-mail Addresses tab.
Click New. Select SMTP Address and click OK.
Fill in the Address field as shown in Figure 7-1. Be sure to include a leading
@before the domain. Click OK.Check the checkbox beside the new SMTP domain to activate it.
If you want the new domain to be the primary (default) domain for all recipients, select it and click Set as Primary.
Click Apply. When you are asked if you wish to apply the change to all recipients, click Yes.
Click OK to close the property sheet.

Figure 7-1. Adding a new SMTP domain to a recipient policy.
Discussion
This is a straightforward task. By default, your Exchange recipients have a single SMTP domain associated with them (their Active Directory domain). By modifying the default recipient policy or creating a new recipient policy, you can add additional SMTP domains to all recipients, allowing your users to share a common domain namespace. This is commonly used to set an organization's recipients to ...