We have a small client who uses an ISP for their email services. One day they decided to change the mail port from 25 to 2525 to try to stop spam. Well, since they've done this many folks (Us included) have been unable to send to them. We just figured this out by chance and then called the client to verify. Telnetting to port 25 of the server yields nothing now since their ISP is now blocking that. Now, the question is how can I configure our Exchange 2003 server to send email to this particular domain over port 2525 without causing issues with the thousands of others we send to?