>try this in your list header:
>
>Subscribe= Open,Confirm
>
>anyone can still subscribe, but they'll have to confirm by
>replying "ok" to a confirmation message from listserv when
>subscribing or unsubscribing.

NO!

For one thing the keyword you refer to is Subscription=, not Subscribe=,
but it ONLY refers to SUBSCRIBE, not UNSUBSCRIBE.  If you want confirmation
for signoffs, you need at least Validate= Yes.  (Under 1.8d it will require
at least Validate= All,Confirm.)

Nathan