WinProxy 4.0 dropping first character on reverse-proxied SMTP server port?!?

From: Nick Marden (nick@marden.org)
Date: 02/23/02 

From: nick@marden.org (Nick Marden)
Date: 23 Feb 2002 11:31:40 -0800

I have WinProxy 4.0Rg1 (aka WinProxy for StarBand) on a Windows ME
box. Using the little configurator whiz-bang, I have set up the
gateway box running WinProxy to forward the port 25 on the public
network (internet) interface to the port 25 of my internal mail
server. Nothing tricky here - a pretty standard configuration for
domains that have their own mail server.

The problem comes when SMTP servers on the Internet attempt to connect
to the mail server port on the gateway's public IP address. It appears
that the first character [sic!] of the conversation sent by the
internal mail server, gets dropped by the firewall. Everything else
behaves normally.

In other words, here's the input when connecting from inside the
firewall, to the SMTP server on the local network:

[user@localhost.mydomain.com] telnet mymailserver.mydomain.com 25
Connected to mymailserver.mydomain.com
Escape character is '^]'
220 mydomain.com Super foo mail server ESMTP -- let er rip

And when you connect from the outside world, you get:

[user@host.oninternet.com] telnet gateway.mydomain.com 25
Connected to gateway.mydomain.com
Escape character is '^]'
20 mydomain.com Super foo mail server ESMTP -- let er rip

Note that what is "220" in the first conversation is "20" in the
second. So, any SMTP server that actually implements the "correct"
SMTP protocol, immediately hangs up after seeing that first line,
because an SMTP server is supposed to greet with "220 ..." when it is
ready for SMTP conversations.

The upshot is, most SMTP servers on the internet can't send mail to
this SMTP server, which sucks for me.

Has anyone seen this behavior? Is there a fix?

Thanks,

Nick Marden
nick-dont-bother-spamming-me-just-use-nick@marden.org

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