Subscription moderation is a simple extension of the ezmlm subscribe mechanism. Once the user has confirmed the subscribe request, a new request is constructed with a different action code. This is sent out to the moderator(s). When a moderator replies with a valid request and cookie combination, the user is subscribed. The user is then also welcomed to the list. Other moderators won't know that the request has already been approved. If other moderators reply to the request, no notification of the duplicate action is sent to the subscriber of the duplicate action. Ezmlm knows that this is a repeat request since the target address is already a subscriber.
The moderators are not informed about the result, unless there was an error (subscribing a target that is already a subscriber is not considered an error). This cuts down the number of messages a moderator receives. Any list moderator knows (or should know) the qmail/ezmlm/unix paradigm: if you're not told otherwise, your command was carried out successfully. This may be counterintuitive to those used to some other operating systems, but in our experience it doesn't take long to get used to the reliability and efficiency of U*ix/qmail/ezmlm.
Subscription moderation is enabled by creating DIR/modsub and adding the subscription moderator to DIR/mod/:
% ezmlm-sub DIR mod moderator@host
To use an alternative basedir for subscription moderators, place that directory name with a leading ‘/’ in DIR/modsub.