Accept PGP-encrypted mail seamlessly and you won't need a privacy policy except for those who like throwing their lifelog at random strangers. Be sure to use PGP/MIME to include the old message in your mailing.

Of course, setting up PGP, let alone remembering the passphrase (gasp) is a lot to ask of the typical user who needs to use his mail client as a text editor.

Otherwise, it's a cute idea, really. Please excuse cynicism.