I like OpenDNS, but was wondering if anyone has experience deploying it for a location with an Exchange installation. I'm concerned specifically about whether any filtering they do would cause problems with reverse DNS lookup that might interfere with the server or the anti-spam (GFI in our case) installation. Thanks for any insights.
EDIT: Just to follow up for anyone who comes across this question, I went ahead and swapped out our ISP's DNS IPs for OpenDNS's in our LAN's DNS forwarders -- took all of a minute and a half -- and it worked fine. We eventually swapped just our mail and spam servers to point to Google DNS rather than OpenDNS only because I was tired of seeing all the mail queries in our OpenDNS reports, and it has worked great this way as well.
We also eventually swapped out our Exchange/GFI setup for Zimbra and an Exim-based mail filter/gateway (MailCleaner, excellent BTW!), and have successfully kept the same arrangement with Google DNS on these servers and everything else forwarding to OpenDNS.