SMTP TLS on Windows not working (hang forever)

[Maloupi]

Problem description

On windows (PHP 7.4 -> PHP 8.2) (no problem on Linux), sending a mail via SMTP with TLS (no problem with SSL) hang forever on stream_socket_enable_crypto in startTLS() in SMTP.php

I think this is because it use tls 1.0 first.
if i force crypto_method to tls 1.1 or 1.2, it works well :

$crypto_method = STREAM_CRYPTO_METHOD_TLSv1_2_CLIENT;

Code to reproduce

define('SMTP_SERVER', '**********');
define('SMTP_PORT', '587');
define('SMTP_ENCRYPTION', 'tls');
define('SMTP_ACCOUNT', '**********');
define('SMTP_PASSWORD', '**********');
define('DEST_ADDRESS', '**********');

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

require 'phpmailersrc/Exception.php';
require 'phpmailersrc/PHPMailer.php';
require 'phpmailersrc/SMTP.php';

$mail = new PHPMailer(true);

try {
    $mail->isSMTP();                      
    $mail->Host       = SMTP_SERVER;      
    $mail->SMTPAuth   = true;             
    $mail->Username   = SMTP_ACCOUNT;     
    $mail->Password   = SMTP_PASSWORD;    
    $mail->SMTPSecure = SMTP_ENCRYPTION;  
    $mail->Port       = SMTP_PORT;    
    
    $mail->setFrom(SMTP_ACCOUNT);
    $mail->addAddress(DEST_ADDRESS);
    $mail->isHTML(true);    
    $mail->Subject = 'Here is the subject';
    $mail->Body    = 'This is the HTML message body <b>in bold!</b>';
    $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';

    $mail->send();
    echo 'Message has been sent';
} catch (Exception $e) {
    echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
}

[Synchro]

TLS protocols don't work like that; it doesn't try different versions in order, but presents all the options as a list. It may be that your Windows machine has a buggy TLS implementation that breaks on some configs. There isn't a built-in way to change this, but you can achieve it by subclassing the SMTP class (like in this example), overriding the startTLS method, and then injecting your instance back into PHPMailer using setSMTPInstance().

Short version:

class mySMTP extends SMTP
{
    public function startTLS()...
}

$mail = new PHPMailer();
$mail->setSMTPInstance(new mySMTP());

You can then carry on as normal.

Note to myself; I need to update the override example to use setSMTPInstance()

[Maloupi]

Thank you