1. I did not make clear some background:
sorry I didn't mention it : OS X 10.7.5, Mail 5.3
and my path was ambiguous, should have been
~Users/.../Library/Application Support/Mail/Scripts.
2. In Tom's reply he gave the Script folder path as
~Users/.../Library/Application Support//Scripts but no such folder exists on my machine
I did check the system Library and found:
disk/Library/Scripts/Mail Scripts where there are many scripts
but in the Mail interface there is no menu item that allows selection of any Scripts
it seems it has been removed…
so my solution is to add the scrip to my Dock, which works, but I have several so it would be nice for a more elegant solution