Actually, Easydiscuss does not have its own registration page, I believe you are referring to this registration page right? https://www.yourdomain.com/component/users/?view=registration&Itemid=101

If so, that is the Joomla registration form and I believe this Acymailing extension does integration with Joomla registration form, perhaps you can consult with the Acymailing developer regarding this and see how it goes?