This is an optional command for SMTP that this class does not support.
This method is here to make the RFC821 Definition complete for this class
and _may_ be implemented in future
Implements from rfc 821: TURN
public function turn()
{
$this->setError('The SMTP TURN command is not implemented');
$this->edebug('SMTP NOTICE: ' . $this->error['error'], self::DEBUG_CLIENT);
return false;
}