This keyword is not available in LISTSERV Lite.
A "Default-Topics=" list header keyword is available to define the initial topics for new subscribers. The syntax is the same as for the SET TOPICS command, except that topic names are separated by commas in the usual fashion and that the first topic may not start with a + or - sign (there is nothing to add to, as this is a new subscription). This is similar to "Default-Options=" in that it does not affect existing subscribers. Users who signed up before topics were enabled on the list are automatically subscribed to all topics.
As with Default-Options=, setting this keyword affects only subscribers who sign up after you set it. If you want existing subscribers to be set to these topics, you must update them manually with a SET listname TOPICS: topics FOR *@* command.