How to allow 3rd party systems to relay SMTP off of an Exchange 2007 Server

The article below, turned out to be very useful, for when you need to configure SMTP Relay, on an Exchange 2007 Server (single server, no EDGE). It’s not as straightforward as it once was, that is for sure, though I like the idea of making it a bit more difficult, to avoid mistakes.

Very good SMTP Relay Reference for Exchange 2007:

• http://msexchangeteam.com/archive/2006/12/28/432013.aspx