title: symfony 3 swiftmalier don't deliver mails
body: <p>I have some issue with swiftmailer on symfony 3 i spend 3 days searching the problem without any result
  I want to send confirmation mail for my web application, the function of sending mails run correctly but the request retun with statut 302 and log error :
  Exception occurred while flushing email queue: Expected response code 220 but got code "", with message "" so the mail is not dilivered</p>
  
  <p>and here is my confugration files</p>
  
  <p>config.yml</p>
  
  <pre><code>swiftmailer:
  transport: '%mailer_transport%'
  host: '%mailer_host%'
  encryption: ssl
  port: 465
  username: '%mailer_user%'
  password: '%mailer_password%'
  spool: {type: memory}
  </code></pre>
  
  <p>parameters.yml</p>
  
  <pre><code>parameters:
  mailer_transport: smtp
  mailer_host: smtp.mail.yahoo.com
  mailer_user: test@yahoo.com
  mailer_password: test
  secret: ThisTokenIsNotSoSecretChangeIt
  </code></pre>
  
  <p>and the maillin action</p>
  
  <pre><code>public function mailingAction()
  {
      $message = \Swift_Message::newInstance()
          -&gt;setSubject('Hello Email')
          -&gt;setFrom('test@yahoo.com')
          -&gt;setTo('testswiftmailer@yopmail.com')
          -&gt;setBody("test mail");
      //$mailer = $this-&gt;get('mailer')-&gt;send($message);
      $this-&gt;get('mailer')-&gt;send($message);
  </code></pre>
  
  <p>and thanks </p>