Using Edge Transport as a mail relay

Another question that popped up during a session last week was how to use the Edge Transport role of Exchange 2007 as an external relay. Thanks to Bharat Suneja for helping to clarify this.

In order to have the Edge Transport server "relay" mail directly, in E2K7 you need to config an "external relay" accepted domain. If you configure an "internal relay" accepted domain, the Edge Transport delivers the message to the internal Hub Transport servers where the Hub Transport server relies on a mail-enabled contact with the correct SMTP address to relay the message onward. Here is the text of what Bharat sent to me.

As far as relaying is concerned, AcceptedDomains can be set up as External Relay domains or Internal Relay domains - in the former scenario mail is received by the Edge and relayed to the destination mail system, in the latter case (for cross-Forest/trusted Forest environments, where Contacts exist in AD for the destination domain) - the Edge relays to the Hub and the Hub delivers to the destination Forest - usually inside the perimeter / over a vpn connection.
http://technet.microsoft.com/en-us/library/bb124423.aspx