In that case it  might be best to change the list so  that errors are set
to  a single  account,  for which  both owners  have  the password.  That
account can  in turn be  set up  to forward the  errors to the  "on duty"
owner. If that person gets sick or  goes on vacation, the other owner can
log in to the "error mail" account and simply change the forwarding.
 
  Eric