A few issues while trying your approach.
In your cron section, it should be "scripts" not "script".
Make sure you give execute permissions on learnspam as well while you are in the file manager.
Do you know if this only works for the main account (SPAM and HAM) or do I have to modify the script to work in all my mail accounts?
I'll let ya know what else I find
Thanks for your effort.
Agix