Example code for caldera_forms_pro_send_local filter See https://calderaforms.com/doc/caldera_forms_pro_send_local/

caldera_forms_pro_send_local-all.php

<?php
/**
 * Use local email system, instead of Caldera Forms pro, for all forms
 *
 */
add_filter( 'caldera_forms_pro_send_local', '__return_true' );

caldera_forms_pro_send_local-single.php

<?php
/**
 * Use local email system, instead of Caldera Forms pro, for a specific form
 *
 */
add_filter( 'caldera_forms_pro_send_local', function( $send, $form_id ){
	//IMPORTANT: Change your form ID here
	if( 'cf124354' === $form_id ){
		return true;
	}

	return $send;
}, 10, 2  );