The web interface offers both methods.  When using a password, it is able
to tell you whether you are on the list or not and to allow you to change
your  subscription  options or  e-mail  address  on the  fly.  Everything
happens synchronously  and without surprise.  When using the  screen that
does not  require a password, the  interface cannot even tell  you if the
address  you typed  is subscribed,  and there  is no  way to  change your
subscription options (because they cannot be queried). You just get a box
in which  you can  type an e-mail  address, then you  click on  "Join" or
"Leave" and it sends you e-mail.

  Eric