Sean Daniel and Adam DePue, both members of the SBS product group,  have put together a blog post on how to host multiple e-mail domains on SBS 2008.So, to set up your primary domain name, please do run the Internet Address Management Wizard.

To set up your secondary (and more) domain, follow these steps:

1. Click Start and point to All Programs and click on Microsoft Exchange Server 2007 and then launch the Exchange Management Console.
2. Expand Organization Configuration and select Hub Transport.
3. On the right, under Actions, click on New Accepted Domain …, and wait for the wizard to pop-up

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