Q&A Plugin - How does subscribe to new questions work?

1. Can you please explain how the "subscribe to new questions" feature works in this plugin?

a. Suppose I have ticked this options for "Subscribers". Will it show an option to the subscribers to receive/unreceive new questions, or will it go to all subscribers by default?

b. In any case, I am not receiving new questions by email in the role of a subscriber.

2. Another related question, how can i allow people to subscribe to specific question category.

Can you please help?