WordPress: Log Emails for Debugging

<?php
/*
Plugin Name: Log Emails for Debugging
Plugin URI: http://www.damiencarbery.com
Description: Log emails sent.
Author: Damien Carbery
Version: 0.4

$Id: wp-mail-logging.php 3641 2016-04-15 17:48:53Z damien $
*/

add_filter( 'wp_mail', 'dbg_log_email_info' );
function dbg_log_email_info( $params )
{
    // If $params['to'] email is an array then implode it into a string.
    if (is_array($params['to'])) {
        $to = implode(', ', $params['to']);
    }
    else {
        $to = $params['to'];
    }
    $log_info = sprintf('To: %s | Subject: %s | Message: %s | Headers: %s', $to, $params['subject'], var_export($params['message'], true), var_export($params['headers'], true));

    // Write to/from/subject of email to a log.
    if (function_exists('debug2log')) {
        debug2log($log_info);
    }
    else {
        error_log($log_info);
    }
    return $params;
}


// From email address is not sent in 'wp_mail' filter so log it via another filter.
add_filter( 'wp_mail_from', 'dbg_log_email_from' );
function dbg_log_email_from( $from ) {
  if (function_exists('debug2log')) {
    debug2log(sprintf('Email from:%s', $from));
  }
  else {
    error_log(sprintf('Email from:%s', $from));
  }
    return $from;
}
?>