Exchange DNS problem

By aaronlandis ·
I recently implemented content filtering using OpenDNS at the company that I work for. So obviously our DNS forwarders have been modified to send everything to OpenDNS servers for host to IP resolution. This causes a bit of trouble for our exchange server though. For some reason OpenDNS feels the need to block outgoing mail to domains that are filtered as well as normal traffic. I don't want my exchange server to have a blind eye to certain domains because there is no way of knowing all of the domains that are blocked and I doubt we'd get much of any indication back that mail did not go through if someone ever did try to send to a blocked domain. Anyway, what tried to do was modify the DNS servers that exchange uses for it's SMTP protocol to our ISP's DNS servers so as to circumvent the use of OpenDNS. I made this change under the advanced delivery options of our smtp virtual server where you have the option to configur external DNS servers. Unfortunately about 24 hours after making this change all outgoing mail started bouncing back. Removing the two entries I made in this area solved the problem but now I'm blind to blocked domains as I'm going through OpenDNS. I would like to have exchange use separate DNS servers without breaking. Any suggestions would be great.

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