List Flag: sub-confirm

Indicates to listmanager that all subscription and unsubscription requests
require confirmation by the intended subscriber, to prevent forged
requests from being used as a form of harrassment by hackers.

Upon receiving an attempt to subscribe or unsubscribe, listmanager notifies
the intended subscriber that it has received the request, but the request
requires confirmation.  A random 32-character code is sent back, which must
be used as part of a "confirm" command to complete the request.  Unconfirmed
requests are deleted after seven days.

See also: confirm sub-approve subscribe