This is integration between SmartResponder and Joomla that allow subscribe to newsletter during registration.
To use this plugin you have to have paid Smartresponder account.
This plugin add new checkbox field on user registration form that allows subscribe user to your smartresponder channel, newsletter, group or series during registration process. You can make this field required if you want to force users to be subscribed. If it is not required users will be able to unsubscribe by editing profile.