Add following code in your theme’s (child theme’s if you are using) functions.php
add_action( 'init', function() {
if ( class_exists( 'Fep_Email_Beautify' ) ) {
remove_action( 'wp_loaded', array( Fep_Email_Beautify::init(), 'announcement_email_send' ), 12 );
}
}, 12 );