We have a mailing list (Google group) at https://groups.google.com/group/hacman. This can be used with the web interface like a forum, or like a mailing list from your usual mail client. From the web interface, the 'My settings' icon in the top right hand corner should guide you through subscribing by email.
To subscribe without a Gmail account, send a blank email to [email protected] (adjust this address for the other Google Groups). When you get the "Join request" email, simply reply to it instead of clicking the link.
If you actually want to unsubscribe then go to this link and you should be able to unsubscribe. If this, for some reason, doesn't work then got to https://groups.google.com/group/hacman then "edit my membership" on the right hand side the click the 'unsubscribe' button on the bottom right. Without a Gmail account, send a blank email to [email protected] from the address you subscribed from.