Run Test for number of recipients:
<ul>
  <li><a href="?n=1">1</a></li>
  <li><a href="?n=10">10</a></li>
  <li><a href="?n=30">30</a></li>
  <li><a href="?n=100">100</a></li>
</ul><br />
<b>Fatal error</b>:  Uncaught exception 'Swift_ConnectionException' with message 'The SMTP connection failed to start [smtp.swiftmailer.org:25]: fsockopen returned Error Number 113 and Error String 'No route to host'' in /var/www/mediathek.mt.haw-hamburg.de/data/lib/vendor/swift/lib/Swift/Connection/SMTP.php:0
Stack trace:
#0 /var/www/mediathek.mt.haw-hamburg.de/data/lib/vendor/swift/lib/Swift.php(0): Swift_Connection_SMTP-&gt;start()
#1 /var/www/mediathek.mt.haw-hamburg.de/data/lib/vendor/swift/lib/Swift.php(0): Swift-&gt;connect()
#2 /var/www/mediathek.mt.haw-hamburg.de/data/lib/vendor/swift/tests/benchmarks/time_sending_with_swift.php(0): Swift-&gt;__construct(Object(Swift_Connection_SMTP))
#3 /var/www/mediathek.mt.haw-hamburg.de/data/lib/vendor/swift/tests/benchmarks/time_sending_with_swift.php(2): sg_load('2B1F8690E2F8904...')
#4 {main}
  thrown in <b>/var/www/mediathek.mt.haw-hamburg.de/data/lib/vendor/swift/lib/Swift/Connection/SMTP.php</b> on line <b>0</b><br />