title: Swift_TransportException (503) Expected response code 354 but got code "503" - Laravel
body: <p>I'm trying to send emails using MS Exchange as smtp Server, that doesn't need any authentication and requires no encryption. this is my (.env) file:</p>
  
  <pre><code>MAIL_DRIVER=smtp
  MAIL_HOST=servername
  MAIL_PORT=25
  MAIL_USERNAME=null
  MAIL_PASSWORD=null
  MAIL_ENCRYPTION=null
  </code></pre>
  
  <p>and the mail.php config file looks like the following:</p>
  
  <p>
  
  <pre><code>return [
  
      /*
      |--------------------------------------------------------------------------
      | Mail Driver
      |--------------------------------------------------------------------------
      */
  
      'driver' =&gt; env('MAIL_DRIVER', 'smtp'),
  
      /*
      |--------------------------------------------------------------------------
      | SMTP Host Address
      |--------------------------------------------------------------------------
      */
  
      'host' =&gt; env('MAIL_HOST', 'smtp.mailgun.org'),
  
      /*
      |--------------------------------------------------------------------------
      | SMTP Host Port
      |--------------------------------------------------------------------------
      */
  
      'port' =&gt; env('MAIL_PORT', 25),
  
      /*
      |--------------------------------------------------------------------------
      | Global "From" Address
      |--------------------------------------------------------------------------
      */
  
      'from' =&gt; [
          'address' =&gt; env('MAIL_FROM_ADDRESS', 'email@domain.de'),
          'name' =&gt; env('MAIL_FROM_NAME', 'Some name'),
      ],
  
      /*
      |--------------------------------------------------------------------------
      | E-Mail Encryption Protocol
      |--------------------------------------------------------------------------
      */
  
      'encryption' =&gt; env('MAIL_ENCRYPTION', 'tls'),
  
      /*
      |--------------------------------------------------------------------------
      | SMTP Server Username
      |--------------------------------------------------------------------------
      */
  
      'username' =&gt; env(null),
  
      'password' =&gt; env(null),
  
      /*
      |--------------------------------------------------------------------------
      | Sendmail System Path
      |--------------------------------------------------------------------------
      */
  
      'sendmail' =&gt; '/usr/sbin/sendmail -bs',
  
      /*
      |--------------------------------------------------------------------------
      | Markdown Mail Settings
      |--------------------------------------------------------------------------
      */
  
      'markdown' =&gt; [
          'theme' =&gt; 'default',
  
          'paths' =&gt; [
              resource_path('views/vendor/mail'),
          ],
      ],
  
      |--------------------------------------------------------------------------
      | Log Channel
      |--------------------------------------------------------------------------
  
  
      'log_channel' =&gt; env('MAIL_LOG_CHANNEL'),
  
  ];
  </code></pre>
  
  <p>This app is running on MS Windows Server 2012 R2 with IIS8, it was working fine locally on my Win10 system but when deployed on the server it started giving this error :</p>
  
  <p><a href="https://i.stack.imgur.com/w3DrS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/w3DrS.png" alt="enter image description here"></a></p>
  
  <p>And when I telnet on the smtp server it gives the following:</p>
  
  <p><a href="https://i.stack.imgur.com/KJtKY.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KJtKY.png" alt="enter image description here"></a></p>
  
  <p>What could be the issue?</p>