caldera-forms-debug-mail-hard.php

<?php
/**
Plugin Name: Caldera Form Mail Debug Helper
Version: 0.1.0
*/

/**
 * Write data to log
 */ 
function cf_mail_debug_write_log ( $log )  {
  if ( is_array( $log ) || is_object( $log ) ) {
     error_log( print_r( $log, true ) );
  } else {
     error_log( $log );
  }
}

/**
 * Log data sent to mailer.
 */ 
add_action( 'caldera_forms_do_mailer', 'cf_mailer_debug_capture_details', 99, 3 );
function cf_mailer_debug_capture_details( $mail, $data, $form ) {
    global $transdata;
    $entry_id = $transdata['entry_id'];
    $log = array( 'entry_id' => $entry_id, 'save_point' => 'pre_send', 'recipients' => $mail[ 'recipients'] );
    cf_mail_debug_write_log( $log );
}

/**
 * Log data from mailer errors.
 */ 
add_action( 'caldera_forms_mailer_failed', 'cf_mailer_debug_capture_failer_details', 10, 3 );
function cf_mailer_debug_capture_failer_details($mail, $data, $form) {
  global $transdata;
    $entry_id = $transdata['entry_id'];
     $log = array( 'entry_id' => $entry_id, 'save_point' => 'pre_send', 'recipients' => $mail[ 'recipients'] );
    cf_mail_debug_write_log( $log );
}