I have a 3rd party that we are using for advertising services, and I'd like to allow them the ability to relay their mail thru one of my SMTP servers. Is this possible? If so, how can this be setup?

If you mean Exchange 2007 /2010, this is explained here: Elan Shudnow's Blog: How Anonymous Relay works in Exchange 2007 http://www.shudnow.net/2008/08/21/how-anonymous-relay-works-in-exchange-2007/ Allowing application servers to relay off Exchange Server 2007 http://msexchangeteam.com/archive/2006/12/28/432013.aspxMCTS: Messaging | MCSE: S+M

Agree with Jon, You must create a new receive connector (Let say application Relay) and configure it according to above URL. Don't forget to check park permission group "Exchange Server" Cheers !!!!Anil