Policy Based Firewall Rules

My Current Mail Server is setup per Below

Router/Firewall > Port 25 Forwarded > Anti-Spam Server > Port 25 Forwarded > Mail Server

what I want to do is add an ISA server or similar machine which can inspect where the origination IP request came from. Then if the Originating machine matches our list it forwards to another server rather than the Anti-Spam Server.

No Match
Router/Firewall > Port 25 Forwarded > ISA Server > Port 25 Forwarded > Anti-Spam Server > Port 25 Forwarded > Mail Server
Router/Firewall > Port 25 Forwarded > ISA Server > Port 25 Forwarded > Secondary Server
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BudDurlandDirector of ITCommented:
Is the secondary server a different domain?  Much easier to jigger with MX records.

I don't think ISA has the smarts to do this.  One of the *nix SMTP transports might, though..

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