Friday, April 30, 2004, 11:33:31 PM, Fernando Sanchez wrote:
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FS> I've noticed that some servers do not allow my server to connect on port
FS> 25 for SMTP, when doing a manual test with:
FS> $ telnet mx.some.server.com 25
FS> from the server it just stays on:
FS> Trying x.x.x.x
FS> but if I try to telnet that remote server from another box on mynetwork
FS> I get the welcome message from the MTA on the other side. Does anybody
FS> have had the same kind of problems? I try to search for my server on
FS> sever black lists but is not on any. I was trying with tcpdump, but
FS> don't know what to look for in the output. Any ideas?
I have had this issue with linux once, failing to connect
to one of ICQ's servers and to lists.netsys.com
(full-disclosure@??? mailing list).
The problem was with ECN, as their servers (ICQ & netsys)
did not support it, and caused their firewalls probably to
drop the packets.
Over the Linux kernel v2.4 tree you will find it at the Networking
category as: "IP: TCP Explicit Congestion Notification support", just
disable it.
HTH, Tomer.
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Tomer H. tomer@???
IT Solutions Provider
www.metnix.com info@???
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