A new keyword has been added in  version 1.5j, as per a suggestion from Alan
Crosswell:
 
           Default-options= opt1,opt2,...
 
  The default list distribution options assigned to a new user upon completion
of  a SUBSCRIBE  or ADD  command are  automatically altered  as though  a "SET
listname  opt1  opt2..."  command  had   been  issued  immediately  after  the
ADD/SUBSCRIBE. The user  is informed about this special set  of options in the
standard ADD mailfile (mailform ':ADD1') for an ADD command, or by message for
a SUBSCRIBE command.
 
  Eric