$SIGNUP isn't technically a template, it's a piece of common text that is
imbedded  with .IM  from the  templates for  ADD and  SUBSCRIBE. LISTSERV
can't "send" you a copy of $SIGNUP because it's just a text include, what
you should be  including in your $SITE$.MAILTPL file  is the higher-level
template you want it to send.
 
  Eric