I am having an issue, which I know what I need to do, but the ways that I have tried opening port 25 do not work. I have a single SBS 2003 server directly connected just to a Comcast business modem, no firewall appliance or anything else.
Now I can telnet to port 25 of external mail server and to my local server address, but if I try to telnet to the public IP its not open.
No I can send email just fine, but of course not receive it since that port is being blocked.
So I made sure using mxtoolbox and microsofts connectivity check, which both failed.
This is what I did, on the modem I tried disabling all port blocking, but that didn't work. I also tried setting up port forwarding, that didn't help either.
I checked to make sure the antivirus wasn't blocking it, and it wasn't, and of course the windows firewall is turned off, so no concern...