Mail.app on Tiger can be specified the default character set with the defaults system link that:
default write com.apple.mail NSPreferredMailCharset ISO-2022-JP
However Mail.app on Leopard has been shipped without the capability of NSPreferredMailCharset.
Simply, LeopardPreferredMailCharset is born to get it back. (And I hope it killed by Apple's official update of Mail.app)
