Exchange Technet links

Managing Connectors
http://technet.microsoft.com/en-us/library/bb125128.aspx

Send Connectors
http://technet.microsoft.com/en-us/library/aa998662.aspx

Configuring Exchange 2007 Hub Transport role to receive Internet mail 
http://msexchangeteam.com/archive/2006/11/17/431555.aspx

How to Configure Connectors for Internet Mail Flow
http://technet.microsoft.com/en-us/library/aa998212.aspx

Exchange Server 2007 Recipient Policies and Accepted Domains 
http://msexchangeteam.com/archive/2006/11/16/431531.aspx

Exchange Server 2007 recipient management one-liners 
http://msexchangeteam.com/archive/2006/09/05/428833.aspx

How to Modify an SMTP E-Mail Address by Using Recipient Policies
http://support.microsoft.com/kb/822447

How to customize the SMTP e-mail address generators through recipient policies
http://support.microsoft.com/kb/285136

Recipient Policies
http://msdn.microsoft.com/en-us/library/aa580723.aspx

Troubleshooting the Recipient Update Service in Exchange Server 2003 and Exchange 2000 Server
http://support.microsoft.com/kb/288807