Save the file to your user's Library -> Scripts -> Applications -> Mail folder, and call it Void Email Trasher.scpt. Then open up Mail, go to Preferences, and click the Rules icon. Create a new rule (give it a description such as "Void Email Trasher"), and set these conditions:
If "any" of the following conditions are met:
- Select "Every Message" from the drop-down menu in the first section.
- Perform the following actions: "Run AppleScript" from the drop-down menu, then click Choose and find Void Email Trasher.scpt where you saved it earlier.
[robg adds:
My apologies for the above -- I tested it, right up to the 'save the rule' step.
I haven't tested the AppleScript, as I have yet to receive an email that would be caught by it.]

