You are able to manually add or remove people as subscribers to a forum. Subscribers will get an email update when a new post is made (although these can be amended in the users messaging settings)
- Select Show/edit current subscribers from the Forum administration block
- Select Turn editing on
- Search for the user or users you want to add in the search field under the potential subscriber selection list
- Choose the user/users and select Add.
To remove users in the subscriber selection list simply select the user and click the remove user button. That user will then move to the potential subscriber column