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I’m experiencing a problem with Exchange 2000 SP2. With
SOME destination domains it can’t send messages but I
have in the queue properties the note “Connection drop by
Remote Host”. Looking in the SMTP log file I find an
entry with the error 451 and the link to
This articles tells about a “Bare LF” to qmail. I cannot
find anything in the knowledge base about this problem.



1. Check the Network configuration of the server. If the machine has
network cards, try disabling and/or removing the card from the OS.
2. Verify that there is not 3rd party product running on this machine that
be manipulating the actual packets.
-IE, Network Interface Card (NIC) Teaming.
—Many vendors have custom solutions that provide network card failure
If this is running, attempt to disable it and see if you continue getting
these errors.
3.) You may want to uninstall/reinstall/reconfigure TCP/IP for the box.
4.) I’d also ensure that you update this server to latest Exchange and
Windows service packs.