Noticed a problem with Forefront Security and OpenDNS. The problem I was having was when using OpenDNS and the Forefront DNSBL checking option the server would block ALL emails. I would get a bounce back with the following in the body:
“Diagnostic code: smtp;550 5.7.1 :18.104.22.168:Client host 22.214.171.124 UnknownDNSName; Mail from IP banned. To request removal from this list please forward this message to firstname.lastname@example.org“.
Turning off the DNSBL and inbound emails would work again. Checking with OpenDNS it turns out there was an issue and Microsoft was working on resolving the issue. It has now been corrected and nothing should be needed to make OpenDNS and Forefront work properly together. If for any reason you still have issue you can add blocklist.messaging.microsoft.com to your VPN Typo Exceptions list under the Advanced Settings in the Dashboard. I tested this out and it did the job.