YES provides the ability to insert X-headers into a message in
much the same way it selects signatures. Don't know which nym service
you're using or how it wants to be talked to, but the usual "Anon-to:"
header and/or double-colon insertion at the top of a message should
be a fairly simple editor function. Let Yarn encrypt it with the
mailer's PGP key and away she goes.
-- Kevin Martin <cannon@nic.com> <brasscannon@compuserve.com>