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