the idea was floated on the anti-spam research group mailing list recently (dec 08) of the possibility of MUA software to offer an "unsubscribe" button when displaying a message with mailing list headers, possibly in place of the existing "This is spam!" button if any.
I filed a feature request with Gmail, and now I'm repeating the idea in this forum; perhaps it will reach and take root in the minds of mod-perl-based webmail system authors.
