"Errors-To:" is not  a standard RFC822 header and not  the correct way to
tell a mailer where to send  delivery errors. Internet mail messages have
two  headers, a  RFC822  header  which is  preserved  as  the message  is
delivered  to the  user,  and a  RFC821 header  which  is discarded  upon
delivery and used by  the mailers to talk to each other.  This is how the
mailers know  to deliver the message  to you even though  the header says
"To: LSTOWN-L".  This RFC821 header  also says where the  delivery errors
should be returned (normally owner-listname@listhost). When LISTSERV gets
the error, it checks the list  header and processes as desired. Many mail
systems (and  in particular  gateways) ignore  the RFC821  error address,
especially when gating to a system that does not support that concept (ie
where errors, replies, and everything  else goes to the "From:" address).
In that case there is nothing you can do.
 
  Eric