Heres' an "easy" way:

1) update list definition

SUBSCRIPTION= OPEN,CONFIRM      

2) note to all subscribers that they will have to resubscribe in the near future

3) DEL listname *@* PW=yourpswd

There are other methods too including the method that requires each subscriber to send to the LISTSERV (not list)


CONFIRM listname

There is a list definition keyword that turns on that requirement but I haven't used it in years since often times, subscribers would send it to the list  (and it would get distributed) and some other subscriber would post to the list a question about the just-broadcasted CONFIRM, or would say back to the list, "yes, I got your message."

/P