I just followed these instructions (which I found in response to a similar question here in EE):
I performed the setup for a specific ip address for a single server on my network (a list server that needs to send email out from an address that is not on our exchange server).
But looking at these instructions, I don't see where I am specifically allowing "mail relay".
And looking at my default Receive Connector on my Exchange 2010 Server, I don't see where I am denying "mail relay".
In Exchange 2003, we specifically listed servers that were permitted to "relay". But I don't see the word "relay" in any of this.
I would really like to understand what is going on here and I already have a lot of links on the subject.
Please do not post a link.
Only answer if you yourself can explain in plain English what is going on (without reference to any links).