wordpress_phpmailer_development.php

<?php
/*
Plugin Name: PHP Mailer Override
Version: 1.0.0
Description: Override config for development environment.
Author: Timothée Moulin
Author URI: https://timothee-moulin.me/
*/

defined( 'ABSPATH' ) OR exit;

if (WP_ENV === 'development' && !is_admin()) {
    // Ensure that we are at the end of the queue to override any other SMTP configuration.
    add_action('phpmailer_init', 'phpmailerdocker_init_smtp', 999);
}

/**
 * Force the development SMTP configuration.
 *
 * @param PHPMailer $phpmailer
 */
function phpmailerdocker_init_smtp(PHPMailer $phpmailer)
{
    // You can also store those values in your config file
    $phpmailer->Host = 'smtp.whateveryouwant.com';
    $phpmailer->Port = 25; // could be different
    $phpmailer->SMTPAuth = false; // depends if you need to authenticate, if true, you must set the following values
//    $phpmailer->Username = ''; // if required
//    $phpmailer->Password = ''; // if required
//    $phpmailer->SMTPSecure = 'ssl'; // 'ssl' enable if required, 'tls' is another possible value
//    $phpmailer->SMTPOptions = array(
//      'ssl' => array(
//        'verify_peer' => false,
//        'verify_peer_name' => false,
//        'allow_self_signed' => true
//      )
//    );

    // force using SMTP
    $phpmailer->isSMTP();
    // use a smaller timeout than default (300)
    $phpmailer->Timeout = 4;
    // print logs in your log file
    $phpmailer->SMTPDebug = 4;
    $phpmailer->Debugoutput = 'error_log';
}