In the file mailster/classes/mailster.class.php find this line around 2153

public function is_verified( $force = false ) {

Add at the top of the function:

mailster_remove_notice( 'verify' );
return true;

Now the registration stuff disappears. Just after line 17 which is public function __construct() {

Add:

update_option( 'mailster_license', '853e9c5a-0d81-4a77-bf50-03936c88681a' );
update_option( 'mailster_email', '[email protected]' );
update_option( 'mailster_username', 'GPL Coffee' );

Replace the license, email, name with whatever you want.