One possibility (which might not be that easy technically) would be to assign a new anonymous ID for each such message through the Penet server.
I was thinking of installing a trivial hack in my remailer, such that upon demand it adds some random (essentially unrepeatable) cruft to the From: line, placing it as a name field so as to have no addressing significance. I believe penet assigns IDs based on this line, so chaining this to a penet-style remailer would provide "hit-and-run" anonymity -- even if the remailer wants nothing of the sort. The social desirability of this could be questioned, but it certainly seems more secure to built pseudonyms on top of something like this (using PGP sigs to provide a solid identity) than through the presently-popular approach. Comments? (Julf?)
Hal Finney
PGP 2 key by finger or e-mail Eli ebrandt@jarthur.claremont.edu