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We currently use an external spam filter service that forwards our incoming mail to our internal exchange server. We have decided to stop this service and use Sophos pure messgage on our exchange server instead.

After requesting the external dns mx record to point to our exchange servers public ip (via NAT) instead of the external filter, internal outlook 2007 clients were unable to connect to their mailboxes and owa would mot connect to the mailboxes either.

I quickly reversed the external change, rebooted he exchange server and all was ok again.

Why were the clients \ owa unable to connect?


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Your internal clients likely cannot reach the external address via NAT. You may want to run a separate DNS server internally to allow clients to resolve the mail server to the internal (actual) IP. Having such a setup may also be helpful for a number of other scenarios.

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