In same at line 444 (1.8c) it sez:

   ********************
   * TO JOIN THE LIST *
   ********************
   .FO ON

   Write to &MYNAMES and, in the text of your message
   (not the subject line), write: SUBSCRIBE &LISTNAME

   .FO OFF

Shouldn't it be
SUBSCRIBE &LISTNAME Firstname Lastname?
                                             /b