Sysadmin wrote:
I have recently noticed a growing problem and am curious if anyone else
is seeing the same. There are certain email servers that I am not able
to reach.
I get a "read timeout error" I used the standard 'telnet mailhost 25`
to troubleshoot and found that I am able to reach certain site just
fine. That being I get the RFC required banner. While others I get
nothing. It started out as some .gov sites (e.g. fernald.gov). But now
we are unable to reach AOL.com as well.
I have even gone as far as looking at the packets with a sniffer. I
DO find differences. The response coming back is different.
The REAL kicker is that the results vary by OS and connect type,
RH8 - LAN connection - doesn't work here but does in another geographic location Windows XP - LAN - 2 different locations - doesn't work Windows XP - Dialup - works MAC OSX - LAN - Location 2 - works
The server used for the test case is running Sendmail 8.1.??. I am running postfix 2.0.19 on Redhat 8.
Anybody seeing this or have any ideas.
Seeing this? No.
Ideas? Yes.
It has nothing to do with the O/S. Most likely it has to do with the IP address of your systems and the related, or lack of, DNS information.
The receiving SMTP servers are most likely doing DNS and reverse DNS lookups. If your systems are not fully registered in DNS there is a fair chance some systems will either timeout or refuse connections.
Regards, Ed
-- "I think the problem, to be quite honest with you, is that you've never actually known what the question is."
--The computer "Deep Thought" in "Hitchhiker's Guide to The Galaxy"
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