451 4.4.0 DNS query failed

Copper Contributor

We are having trouble sending email to a specific domain stating that the DNS query failed.  I have verified from the server that I can query the DNS for mx record and can also connect to both mx servers on port 25.  I am able to send an email using smtp commands through command prompt.


However exchange 2010 sp3 RU24 will not try and send.  I have rebooted the Hub server and still won't send?


Any suggestions?

1 Reply
Hi Ace95Hockey,

On the MMC, select your Exchange server(s) that is in the send connector list and go to properties.
1)Go to External DNS lookups tab, under the 'Use these DNS servers' manually add your DNS servers or try with (make sure you have DNS port open to in this case)
2) On the Send connector, go to properties, on the 'Network' tab, check the 'Use the external DNS lookup settings on servers with the transport roles' option and save.
3) Restart the Transport service and see.