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GlennCameron

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Email fails to specific domain with '421 4.2.1 Unable to connect'

We have a simple Exchange 2010 single server setup. Everything has been running fine for years. We have one domain that we are attempting to send an email to that fails. All other emails are flowing fine. The error in the queue is:

451 4.4.0 Primary target IP address responded with: '421 4.2.1 Unable to connect' Attempred failover to alternate host, but did not succeed. Either there are no alternate host, or delivery failed to alternate hosts.

The last successful message to this domain was about 8 weeks ago. I can do an nslookup on the MX records and see them there. I have done an mxtoolbox.com backlist check on my domain and that is coming back fine.

Ideas?

Thanks
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Dave Baldwin
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The usual thing is to 'telnet' to their mailserver and see if it responds.  Or if there is a contact email address, you could try to send them an email thru Yahoo or Gmail to see if they're still there.
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GlennCameron

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I cannot telnet to the mail server. I get 'Connecting to xxxx' then 'Connect failed'.
FYI the domain is a US state government department so they're still there :-)
Their IT is saying that's its an issue on our server.

Thanks
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lindento

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I have done the mxtoolbox.com mx check and they appear to be correct. Was going to try the telnet from home tonight.

Thanks
I cannot telnet to the server either inside my corporate network or at home. Two completely different ISPs and of course no firewall at home.
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The destination company finally admitted that they were blocking the traffic.
Interesting.  Did they say why?
Spam attack from somewhere in China so they have put a lot more restrictions in place. You would of thought that they could have told us that when we first raised the issue!