[Flow] TYPO3/SwiftMailer logs messages but does not send it...

[Jan Greth]

Hi at all,

I have the following problem with the TYPO3.SwiftMailer Package.
Installed it via composer with:

[...]
    "require": {
         [...]
         "typo3/swiftmailer": "dev-master",
         "swiftmailer/swiftmailer": "5.0.*"
     },
[...]

When I use it with Setting:

TYPO3:
   SwiftMailer:
     transport:
       type: 'TYPO3\SwiftMailer\Transport\LoggingTransport'
       options: []

and Code:

$mail = new \TYPO3\SwiftMailer\Message();
$mail->setFrom(array('my at email.com' => 'ME'))
      ->setTo(array('my at email.com' => 'ME'))
      ->setSubject('New comment')
      ->setBody('Hallo', 'text/plain');
$mail->send();

I can find the following in my System log:

[...]
14-10-02 13:12:55 7915       DEBUG     SwiftMailer          Sent email 
to ME <my at email.com>
     message => Message-ID: <73689d67072bc274a5b673d06fb09573 at flow>
Date: Thu, 02 Oct 2014 13:12:55 +0200
Subject: New comment
From: ME <my at email.com>
To: ME <my at email.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

Hallo

[...]

But when I switch settings to real sending with Settings yaml:
TYPO3:
   SwiftMailer:
     transport:
       type: 'Swift_MailTransport'
       arguments: ~
       options: []

Nothing gets sent. What can be wrong there? The mail adress is my real 
one in my code.
Is there anything else to configure to get mailing to work?
Did i miss something?

System is Flow 2.2.2 on a Ubuntu Server with PHP5 and MySQL.

Greetings, Jan