You shouldn't consider e-mail any more "reliable" than US postal mail.
Oh yes, and assume that all US postal mail is generated using typewriters
too. :) If something shows up in your mailbox (postal that is), you
really don't know that it's what it claims to be. The same is true of
e-mail. Anything you want to rely on for verifying the validity of the
mail can be spoofed, just like with postal mail. And LISTSERV doesn't
have any magic-tricks to allow it to tell any better than you do.
-jj