Unable to telnet to port 25 remotely (Windows SMTP)
Setting up the SMTP & POP3 service on Windows 2003, I noticed that I could telnet localhost 25 on remote desktop, but not telnet port 25 remotely.
This turned out to be a setting in the Windows SMTP service. Just Open IIS, Right click properties on Default SMTP virtual server, then Access, connection and
select “All except list below”. Then I can telnet in, and the email started working 🙂