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    <h3>Editing: EsmtpTransport.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Mailer\Transport\Smtp;

use Psr\EventDispatcher\EventDispatcherInterface;
use Psr\Log\LoggerInterface;
use Symfony\Component\Mailer\Exception\TransportException;
use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
use Symfony\Component\Mailer\Transport\Smtp\Auth\AuthenticatorInterface;
use Symfony\Component\Mailer\Transport\Smtp\Stream\AbstractStream;
use Symfony\Component\Mailer\Transport\Smtp\Stream\SocketStream;

/**
 * Sends Emails over SMTP with ESMTP support.
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 * @author Chris Corbyn
 */
class EsmtpTransport extends SmtpTransport
{
    private array $authenticators = [];
    private string $username = '';
    private string $password = '';
    private array $capabilities;

    public function __construct(string $host = 'localhost', int $port = 0, bool $tls = null, EventDispatcherInterface $dispatcher = null, LoggerInterface $logger = null, AbstractStream $stream = null)
    {
        parent::__construct($stream, $dispatcher, $logger);

        // order is important here (roughly most secure and popular first)
        $this-&gt;authenticators = [
            new Auth\CramMd5Authenticator(),
            new Auth\LoginAuthenticator(),
            new Auth\PlainAuthenticator(),
            new Auth\XOAuth2Authenticator(),
        ];

        /** @var SocketStream $stream */
        $stream = $this-&gt;getStream();

        if (null === $tls) {
            if (465 === $port) {
                $tls = true;
            } else {
                $tls = \defined('OPENSSL_VERSION_NUMBER') &amp;&amp; 0 === $port &amp;&amp; 'localhost' !== $host;
            }
        }
        if (!$tls) {
            $stream-&gt;disableTls();
        }
        if (0 === $port) {
            $port = $tls ? 465 : 25;
        }

        $stream-&gt;setHost($host);
        $stream-&gt;setPort($port);
    }

    /**
     * @return $this
     */
    public function setUsername(string $username): static
    {
        $this-&gt;username = $username;

        return $this;
    }

    public function getUsername(): string
    {
        return $this-&gt;username;
    }

    /**
     * @return $this
     */
    public function setPassword(#[\SensitiveParameter] string $password): static
    {
        $this-&gt;password = $password;

        return $this;
    }

    public function getPassword(): string
    {
        return $this-&gt;password;
    }

    public function addAuthenticator(AuthenticatorInterface $authenticator): void
    {
        $this-&gt;authenticators[] = $authenticator;
    }

    public function executeCommand(string $command, array $codes): string
    {
        return [250] === $codes &amp;&amp; str_starts_with($command, 'HELO ') ? $this-&gt;doEhloCommand() : parent::executeCommand($command, $codes);
    }

    final protected function getCapabilities(): array
    {
        return $this-&gt;capabilities;
    }

    private function doEhloCommand(): string
    {
        try {
            $response = $this-&gt;executeCommand(sprintf(&quot;EHLO %s\r\n&quot;, $this-&gt;getLocalDomain()), [250]);
        } catch (TransportExceptionInterface $e) {
            try {
                return parent::executeCommand(sprintf(&quot;HELO %s\r\n&quot;, $this-&gt;getLocalDomain()), [250]);
            } catch (TransportExceptionInterface $ex) {
                if (!$ex-&gt;getCode()) {
                    throw $e;
                }

                throw $ex;
            }
        }

        $this-&gt;capabilities = $this-&gt;parseCapabilities($response);

        /** @var SocketStream $stream */
        $stream = $this-&gt;getStream();
        // WARNING: !$stream-&gt;isTLS() is right, 100% sure :)
        // if you think that the ! should be removed, read the code again
        // if doing so &quot;fixes&quot; your issue then it probably means your SMTP server behaves incorrectly or is wrongly configured
        if (!$stream-&gt;isTLS() &amp;&amp; \defined('OPENSSL_VERSION_NUMBER') &amp;&amp; \array_key_exists('STARTTLS', $this-&gt;capabilities)) {
            $this-&gt;executeCommand(&quot;STARTTLS\r\n&quot;, [220]);

            if (!$stream-&gt;startTLS()) {
                throw new TransportException('Unable to connect with STARTTLS.');
            }

            $response = $this-&gt;executeCommand(sprintf(&quot;EHLO %s\r\n&quot;, $this-&gt;getLocalDomain()), [250]);
            $this-&gt;capabilities = $this-&gt;parseCapabilities($response);
        }

        if (\array_key_exists('AUTH', $this-&gt;capabilities)) {
            $this-&gt;handleAuth($this-&gt;capabilities['AUTH']);
        }

        return $response;
    }

    private function parseCapabilities(string $ehloResponse): array
    {
        $capabilities = [];
        $lines = explode(&quot;\r\n&quot;, trim($ehloResponse));
        array_shift($lines);
        foreach ($lines as $line) {
            if (preg_match('/^[0-9]{3}[ -]([A-Z0-9-]+)((?:[ =].*)?)$/Di', $line, $matches)) {
                $value = strtoupper(ltrim($matches[2], ' ='));
                $capabilities[strtoupper($matches[1])] = $value ? explode(' ', $value) : [];
            }
        }

        return $capabilities;
    }

    private function handleAuth(array $modes): void
    {
        if (!$this-&gt;username) {
            return;
        }

        $authNames = [];
        $errors = [];
        $modes = array_map('strtolower', $modes);
        foreach ($this-&gt;authenticators as $authenticator) {
            if (!\in_array(strtolower($authenticator-&gt;getAuthKeyword()), $modes, true)) {
                continue;
            }

            $code = null;
            $authNames[] = $authenticator-&gt;getAuthKeyword();
            try {
                $authenticator-&gt;authenticate($this);

                return;
            } catch (TransportExceptionInterface $e) {
                $code = $e-&gt;getCode();

                try {
                    $this-&gt;executeCommand(&quot;RSET\r\n&quot;, [250]);
                } catch (TransportExceptionInterface) {
                    // ignore this exception as it probably means that the server error was final
                }

                // keep the error message, but tries the other authenticators
                $errors[$authenticator-&gt;getAuthKeyword()] = $e-&gt;getMessage();
            }
        }

        if (!$authNames) {
            throw new TransportException(sprintf('Failed to find an authenticator supported by the SMTP server, which currently supports: &quot;%s&quot;.', implode('&quot;, &quot;', $modes)), $code ?: 504);
        }

        $message = sprintf('Failed to authenticate on SMTP server with username &quot;%s&quot; using the following authenticators: &quot;%s&quot;.', $this-&gt;username, implode('&quot;, &quot;', $authNames));
        foreach ($errors as $name =&gt; $error) {
            $message .= sprintf(' Authenticator &quot;%s&quot; returned &quot;%s&quot;.', $name, $error);
        }

        throw new TransportException($message, $code ?: 535);
    }
}
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