I have an SMTP virtual server installed on Windows
2000/IIS 5 server (patched except for yesterday's updates).
As of a few days ago, it successfully sent mail to all
recipients. A few days ago, it stopped sending mail to
one domain--I'll call it domain z.com.
The mailserver for z.com also accepts mail for x.com and
y.com. Messages sent from the SMTP server to these other
domains is delivered successfully.
From the SMTP server, I ran nslookup and resolved z.com
successfully. Yet, messages to z.com sit in the SMTP
server's queue and in the system log--
"Event ID 4000 SMTPSVC : Message delivery to the remote
domain 'z.com' failed for the following reason: The remote
server did not respond to a connection attempt."
I used Network Monitor to capture traffic from the SMTP
server while generating email to x.com, y.com, and z.com.
I saw the SMTP server query DNS for x.com and y.com but no
attempts to resolve z.com. I ran netMon again and only
sent to z.com--nothing. The message queued but I saw no
traffic. ??
The SMTP server seems to make no attempt to resolve the
z.com or deliver the messages. The network segment that
is home the the SMTP server is an NT 4 domain with no
internal DNS. The SMTP server uses the DNS resolvers
assigned by our ISP.
I am stumped. I have no idea what to try next. Thanks for
suggestions!
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