But the  original question was not  about privacy and encryption.  If you
are  going to  discuss an  issue which  for some  reason requires  a good
measure of  confidentiality on a mailing  list, the issue is  not keeping
the discussion within  the list confidential but  preventing normal users
from finding out  who is posting what, who  is on the list, and  so on. I
don't  see how  encrypting  the text  could help,  and  the PEM  business
doesn't encrypt the headers.
 
It all depends on the degree  of security you need. Listening to Internet
lines is pretty easy, so if you're worried about people with that kind of
approach you just can't use the  Internet to discuss such issues, because
it isn't a safe network. Again, encryption  will not help as it isn't the
text which is confidential, but the name of the person who sent it. While
mail headers  can be  forged easily  (this time with  a good  reason), it
would still  be possible for  someone with enough determination  to trace
the forgery  to the  host that did  it, unless it  were done  really very
professionally  (and we  wouldn't  want such  high-quality forging  tools
available  to the  masses with  a nice  click-and-forge interface,  would
we?). If you can trust people, computers  and lines at your site, you can
arrange for the  anonymous mapping to be performed there  and hackers can
listen all they want to the backbone lines. On the other hand, I'm pretty
sure that if you fill up one of these anonymous mailboxes you will sooner
or later  get a message  back from a  mail daemon saying  "imail: unknown
imail error -22987437" with the actual address in it ;-)
 
If on  the other hand  your concern is that  your name and  address would
show on the list, there are anonymous servers for that.
 
  Eric