Block incoming email EXCEPT for specific IP range

I am looking to block my Exchange 2000 server from receiving email from anyone except for a specific IP range.  The problem is that I am receiving a ton of spam that apparently is coming to the server by IP address rather than by MX record.  My MX record actually points to a hosted spam filter and looking at the headres, the emails are not coming from the spam filter host.  I want to restrict my Exchange 2000 server from accepting email from anyone but my spam filter host.  Anyone know how to do this?
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Stacy SpearConnect With a Mentor President/Principal ConsultantCommented:
Exchange 2000 didn't have connection filtering I believe. Check the properties on the smtp virtual server. Access tab, is there a connection control there? If so, add your hosted spam filter there and give it a test.
perk83Author Commented:
Yes, it does have that.  I wasn't sure if that might prevent computers on my network from accessing the server as well.
tigermattConnect With a Mentor Commented:
You can safely configure the SMTP connection control as darkstar has mentioned. It won't affect your computers which have Exchange accounts configured in Outlook, although it will if you have any users connecting to Exchange with POP/IMAP and SMTP through this particular virtual server. The easiest way to get around this if it's an issue is to make another virtual server which has Anonymous authentication disabled and relay enabled; this means users must authenticate to send mail out but it will stop spammers using it as an open relay.

Obviously if you don't have any POP/IMAP clients then this won't be a problem for you. One thing which is often overlooked is dummy POP3 accounts though, they send out via SMTP so may cause you problems. Again, implementing the changes will get around this.

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Stacy SpearPresident/Principal ConsultantCommented:
tigermatt is spot on, normal exchange clients won't even notice, except for the reduction in inbound spam! You shouldn't be doing pop/imap anyway with Exchange.
perk83Author Commented:
Thanks for the help guys.  I split the points as it seemed like the only thing to do since you were both willing to help me out in a time of need.  darkstar3d received the bulk of the points for initially providing the solution.
Thanks :-)
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