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E2K SMTP Connec. Cannot bind to DNS

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4 replies

by jedavidow

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We are unable to send mail to the internet.

All messages eventually end up in the "Destination Unreachable" Queue, and the connector queue displays the message:
"Unable to bind to the destination server in DNS."
on it's properties tab.

I have no idea what's going on. Any ideas?

4 replies

by curlergirl

It certainly sounds as if something is wrong with your DNS setup. Do you have an internal DNS server for your local network? How is your zone set up? Is this DNS server authoritative for your domain or are you forwarding to an ISP's DNS server(s)? If you are using private IP addresses internally, you need to be sure DNS is set up to be authoritative only for your local (internal) domain and use your ISP's DNS servers as forwarders. You can force your Exchange SMTP virtual server to use an external DNS server for sending email by going to the properties of the SMTP Virtual Server, click the Delivery tab, then click the Advanced button, then click the Configure button next to the words "Configure external DNS servers:". Then in that box click the Add button to add your ISP(s) DNS server addresses to force these servers to be used for name resolution. Hope this helps!

by jedavidow

Is there a reason this would suddenly stop working? I just tried adding the servers, but it's not helping. Any other ideas?

by shmaltz

On the Exchange Server open a command prompt and type the following (make sure that you type exactly since nslookup is case sensitive when it comes to coammnds):
nslookup
set type=MX
yahoo.com

If you get an answer after the last line then DNS is not the problem. If you get an error or it can't resolve it then DNS is your problem. Configure your Exchange Server with a valid DNS and the problem should be gone.

by jedavidow

First, the connector is set up with a smart host. So really, DNS should not be a problem. I will check the DNS lookup for that MX record though...

I was able to temporarily solve this by entereing the IP number of the smart host in both the connector and in the advanced dialog of the Delivery options on the SMTP server. (This is not a good solution- there are several SMTP servers in use by our ISP, and I am not sure their IP#s are always in use).

Is there any reason that the server would have trouble looking up the smart host's IP?

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