Exchange 2000`

I am using exchange 2000 for a small to mid-sized company. Over the weekend we seem to have had some problems with or exchange server.

SMTP seems to not want to let any new messages in. I have restarted all the exchange services and rebooted, and still nothing. We can send and receive internal messages , but just no external. could someone point me in the right direction of getting this fixed.

Thanks

JKL