How to Configuring Exchange to receive email from multiple domains?

1. Start Exchange System Manager.
2. Click to expand the Recipients container.
3. Click Recipient Policies.
4. Open the properties of the appropriate policy that is displayed in the right pane.
5. Click the E-Mail Addresses tab, and then add any additional Simple Mail Transfer Protocol (SMTP) addresses that you want the Exchange-based computer to host. For example, to add a new SMTP mail domain, follow these steps:
1. Click New, click to select SMTP Address, and click OK.
2. In the Address box, type the at sign (@) followed by the name of the SMTP domain.

For example, to accept mail for Contoso.com, type the following in the Address box, and then click OK:
@contoso.com
6. Your new address space is now listed on the E-Mail Address tab. To enable your new address space, click to select the check box next to the address that you created, and then click OK.