About 48 hours ago our Exchange 2003 server on a Windows Server 2003 Standard Edition stopped receiving emails from outside domains. Internal email are sent and received just fine and we can send emails out to different domains. Our email comes in through a SonicWall A200 Email Security Appliance which has been installed for 6 months.

Nine days ago I changed the DNS and IP address of our email server because of an issue of emails being marked as spam by a local provider. That didn't solve the problem so two days later I changed it back to the original settings both DNS and on the SonicWall 2040 Internet Security Appliance. Everything continued to work fine until five days later when we stopped receiving outside domain emails.

I've ran TraceRoutes, DNS Lookups and everything looks good from those websites. I've restarted the server several times and restarted the MS Exchange Information Store a few times as well. When I look at the A200's Auditing it shows email messages coming in and being marked properly as spam, phishing, etc. But good emails as soon as they come in are marked as queued and then seconds later marked as bounced. When I look at the message detail in the A200 it has good emails marked as Good. So it appears that Exchange isn't accepting the emails or the A200 isn't actually passing the emails on.