I have an SBS2008 server with the default install for Exchange. I have a select few domains in the queue with 451.4.4.0 DNS query failed while the rest of the mail flows properly. I do have forwarders in DNS configured.
I removed the forwarders, restarted DNS, and tried a retry with no success. I used nslookup set type=mx and it did resolve. When I telnet to port 25 I receive 220 ..domainname.. ESMTP (that is the extent of my knowledge when using telnet to port 25).
I ran the mail flow troubleshooting assistant with the category "messages are backed up in one or more queues". It noted a mail acceptance failure -..... MAIL FROM command: Respond = 501 #5.0.0 EHLO requires domain address
It issued a couple of warnings -- Remote server.... does not support the 8BITMIME verb. This will prevent routing of mails requiring the 8BITMIME extension. Please check whether the queue contains such messages.
Remote server.... refused the test mail to recipient SERVERNAME-SA@domainname.com'. If this remote server belongs to a remote domain, this is not necessarily indicating a problem. RCPT TO command: Respond = 550 5.7.1 Unable to relay for [email=SERVERNAME-SA@domainname.com]SERVERNAME-SA@domainname.com[/email].
I have been unable to find a solution and of course, mail delivered fine last week with SBS2003 to the same domain.
One of the guys I work with mentioned they had found an article that stated when your forwarders in DNS do not point to your ISP DNS servers you need to manually set DNS in Exchange to your ISP DNS servers. This happens to be the case on this server so I entered the ISP DNS servers inside Exchange and the queue cleared. Mail seems to be flowing properly.
I seen to be experiencing the same issue but only to 1 particular domain. The MX record resolves with no issue and I can telnet to the hosts and perform test messages from the same Exchange server. I tried setting to the ISP DNS servers as well as using the root DNS but neither seems to resolve the issue. The MX record does return an alias from a different domain but I don't think that should be an issue. Any help would be appreciated. The server is running SBS2008 (Exchange 2007).
Posts: 2271
Joined: 12.Apr.2008
From: The Netherlands
Status: offline
Hi,
For the 8bitmime issue there are two solutions:
- upgrade Exchange 2007 to SP1 - create a seperate connector for the domain and publish a 7bitmime, this can be done by executing the following Powershell command:
New-SendConnector -Name Test -AddressSpaces testdomain.com - ForceHELO $true
I tried creating the separate send connector as you specified and still no luck. Already had the SP1 installed. it seems as if the issue is in resolving the domain based on the error message. Why would it give a DNS query failed message?
I had tried that and it does respond. I can even telnet and submit a test message using the DNS entry from the server. That is why the a DNS error does not seem to make any sense.
Unfortunately I had tried that as well and it did not work either. I tried putting it in as both the IP and the host name unless I did something wrong when configuring it.
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All Forums >> [Microsoft Exchange 2007] >> Message Routing >> 451.4.4.0 DNS query failed 
451.4.4.0 DNS query failed - 
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