Telnet port 25 problems from Windows Server 2003

[itadmin88]

I have an Exchange Server 2003 running on a Windows 2003 Server and two other Windows 2003 Servers on my network as well as about 50 workstations. All machines are behind a sidewinder firewall that NATs incoming SMTP traffic to the Exchange Server's "internal" (actual) address and all outgoing SMTP traffic NATs to the Exchange Server's "external" (virtual) address.

The problem I am having is when I Telnet via Port 25 from the Exchange 2003 Server to any other mail server on the internet, it connects but immediately closes the connection. As soon as I connect and type the first letter of a command (ehlo, hello etc) I receive a "connection to host lost" reply. This also happens from one of the other Windows 2003 Servers.

However, I can successfully Telnet over port 25 from all the workstations and one of the Windows 2003 Servers to mail servers on the internet and can type commands and get proper responses without the connection immediately closing. If this was only happening from my Exchange server, I would think it was an Exchange or Firewall issue, however since it also happens from another one of my 3 Windows 2003 Servers it leads me to believe it may be a Windows 2003 Server issue. Again, all machines are behind the same sidewinder firewall and the Windows Firewall is disabled on all machines.

Any suggestions or help is greatly appreciated.

 

[Zelandakh]

I'd say it is a firewall issue. I don't know the sidewinder but I don't know how Windows could have a problem.

 

[itadmin88]

I would agree it is a firewall issue IF it affected all the machines behind the firewall but I am only seeing this behavior on two of the Windows 2003 Servers. A third Windows 2003 Server and all workstation are not experiencing this issue and all are behind the same firewall.

 

[N0ktar]

I would simply test telnet 25 from inside of your network first and make sure the SMTP service works properly before troubleshooting any firewall issues.

 

[Zelandakh]

But this is outbound connectivity to external boxes not SMTP service troubles from the look of it.