Mail Rule fails – how to see why or how to debug?

I’ve a Mail rule that sometimes fails with an AppleScript error. Where does macOS report such errors? Is there a log file? And how can I debug Mail rules with SD?

I took me hours to realize that Mail rules don’t work when I use the Foundation Framework but I don’t know why as I can’t see the error message.

I’ve to answer myself :smiley:

After forcing a known failure I’ve found out how the error appears in the Console app:

You’ve to search for msg:Failed execution of AppleScript