Using a Mail rule to run an AppleScript

Question

I've been trying to get a Mail rule to run a very simple AppleScript on 10.5.3 and it just doesn't work, period.
I've tried making everything as simple as possible:
1. My Mail rule sets the background color of a message and runs the AppleScript if the subject contains "test".
2. The AppleScript displays a Finder alert.
[(screenshot)|http://i26.tinypic.com/nqxou8.png]
Naturally, the script runs fine within the Script Editor. I also know that the rule works since the background color action gets applied.
But, the AppeScript never runs when I apply the rule to a message manually or when it gets automatically applied to new messages. I really can't imagine where I'm going wrong here...

Answer 1

You can't simply feed it some arbitrary script to execute, you have to write a handler that Mail can dispatch events to. This generally looks something like
using terms from application "Mail"
on perform mail action with messages theMessages for rule theRule
tell application "Mail"
repeat with suspectMessage in theMessages
--do something
end repeat
end tell
end perform mail action with messages
end using terms from