I've set up a SMTP server using IIS 6 on Windows Server 2008. I've set it up for "All Unassigned" IP adresses on port 25. I've also added and the IP to the extrenal source in the "Relay". I've configured the Windows Firewall to accept port 25.

I am able to connect to smtp with telnet localy but not external from the IP I've added to the relay. I get the message: "Could not open connection to the host, on port 25: Connect failed"

A port scan shows that port 25 is open on the server.

Any idea what the issue might be, and how to fix?


You mentioned that you put the external IP address from which you want to access the SMTP server in Relay settings, but you didn't mention the Access or Connection settings.

Go to the properties of your SMTP Virtual Server. Click the Access tab. Click the Authentication button. Make sure that anonymous access is checked. Hit OK.

Now go down to the Connection button. Make sure that the IP addresses from which you want to access the SMTP relay are granted access. Hit OK.

Now go down to the Relay button. Again make sure that the IP addresses you want to connect from are granted access here as well. Hit OK.

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  • Thanks for the reply Ryan and taking the time with the screen shots! I'm sorry that I forgot to mention but I've already did this (and double checked to be sure). The reply is nice and useful so I'll give it a vote for that (edit: when I have enough in reputation) :) – Arne H. Bitubekk Feb 18 '13 at 14:18
  • Are you sure that the external computer is allowed to send traffic on port 25 outbound? A lot of ISPs block it. – Ryan Ries Feb 18 '13 at 14:29

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