FW: What the heck? Telnet to SMTP...

  • From: "Chris Wall" <Chris.Wall@xxxxxxxxxxxxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Thu, 28 Jul 2005 12:03:48 -0400

Never mind -  I think the PIX is the culprit.  Time to have a little
talk with the Network Admin :-)


See here for info - http://www.mcse.ms/message1257982.html





From: Chris Wall 
Sent: Thursday, July 28, 2005 11:59 AM
Cc: [ExchangeList]
Subject: What the heck? Telnet to SMTP...


Hello all,


I have a weird one here.  I have two SMTP Gateway boxes for our
organization.  One is Win 2003 Server with IIS and the other is Win 2000
Server with IIS.  Neither of these servers have Exchange installed, but
they do act as Smart Hosts for our Exchange 2003 environment.


I have just found out that when someone (externally) attempts to telnet
to our SMTP hosts ( and the following




If I attempt to type 'EHLO' or 'HELO' I receive the following:


500 5.3.3 Unrecognized command



If I attempt to telnet to these servers from an internal PC, using the
internal IP address, I get the standard:


220 mail1.globalknowledge.com Microsoft ESMTP MAIL Service, Version:

1 ready at  Thu, 28 Jul 2005 11:53:55 -0400


When typing 'HELO' or 'EHLO' I get the normal reply:



250 mail1.globalknowledge.com Hello []


Mail is flowing as it should into our organization, but I am unable to
successfully force a Telnet Session to our servers from an external
computer.  In the past, our servers have responded to telnet requests as
if internal, but now they respond with '220 *************' etc.  


What could be causing this since I have not made any changes to the IIS
SMTP config?


Any help is greatly appreciated.




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