Our internet connection is a Fractional T1 with a 368K port speed. The
server is currently behind a cisco2600 router running Cisco's firewall
software. The router is also acting as a proxy server and translating my
true internet address to our internal 192.168.x.x network. I do not have
great experience with the router, but am told that it is configured
correctly to allow the following ports from any IP address through to the
server POP3 (110), SMTP(25), 8383 (Imail's Web Interface).
All these ports seem to work correctly most of the time, occassionally a
dial-up client (it almost always seems to be a Mindspring user) is not able
to access a given sub-set of ports. For instance this morning the
difficulty was on SMTP. I was finally able to duplicate the problem and on
my workstation. After connecting to Mindspring I was not able to open an
SMTP session with the server Either through Outlook, or telnetting to port
25. In both Outlook and Telnet the error message was "Server not found". I
could however get through on all the other ports.
While this was happening I contacted our Router specialist and he was able
to telnet to the server on port 25 (through a different ISP over his T1)
directly into the router, his connection was reliable, consistent, and
repeatable. This morning I was never able to get a connection on port 25
(all other ports responded just fine), the router configuration has not
changed and it worked perfectly on Tuesday through Mindspring when I tried
to re-create the issue.
I used Windows95's netstat command to see what state my connection was
getting to, and it never went past a syn-sent. It definetly appeared that
the server was not responding or at least not receiving the request.
Does anyone have any ideas on where this problem might lie? Do I need to
open up additional ports to the server? Could it be something with
Mindspring (perhaps they are filtering my packets)? Mindspring claims they
are providing a true IP connection and that nothing funny should be
happening in their network, but the I really don't know if the tech I spoke
to on the phone is a reliable source.
Any help would be appreciated, at this point I am not sure what to try next.
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