It uses two mandatory parameters - a command and a list name, plus e-mail address option. The button operates a mailto: action to send the form off to a Tristero server. No scripts or direct server access is required for operation of this form.
An example input field is:-
INPUT NAME="LIST" TYPE=TEXT SIZE=20
Fixed parameters may be preset, for example, to allow subscription to only one list with a single button press and no parameters, by using hidden input types, e.g.:
INPUT NAME="LIST" TYPE=HIDDEN VALUE="sales-list"
The form action is coded as:-
FORM ACTION="mailto:listproc@tristero.test.com" METHOD="POST"