How to stop all emails?

There is no global setting to disable them, but with code, if you can add it somewhere, it is.

add_filter( 'giveasap_send_registered_email', '__return_false' ); is for the default subscribe email that each subscriber receives when it signs up.

As for other emails such as notify the admin on each new subscriber or for notifying users when they have received extra points by referring others, those are disabled by default under Giveaways > Settings.

Worked Perfecly. Thank you.