in laRAVEL 5.4 ERROR
C:\xampp\htdocs\itis_db\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport\StreamBuffer.php
and find out this function inside StreamBuffer.php
private function _establishSocketConnection()
and paste this two lines inside of this function
$options['ssl']['verify_peer'] = FALSE;
$options['ssl']['verify_peer_name'] = FALSE;
and reload your browser and try to run your project again. For me I put on like this:
private function _establishSocketConnection()
{
    $host = $this->_params['host'];
    if (!empty($this->_params['protocol'])) {
        $host = $this->_params['protocol'].'://'.$host;
    }
    $timeout = 15;
    if (!empty($this->_params['timeout'])) {
        $timeout = $this->_params['timeout'];
    }
    $options = array();
    if (!empty($this->_params['sourceIp'])) {
        $options['socket']['bindto'] = $this->_params['sourceIp'].':0';
    }
   $options['ssl']['verify_peer'] = FALSE;
    $options['ssl']['verify_peer_name'] = FALSE;
    $this->_stream = @stream_socket_client($host.':'.$this->_params['port'], $errno, $errstr, $timeout, STREAM_CLIENT_CONNECT, stream_context_create($options));
    if (false === $this->_stream) {
        throw new Swift_TransportException(
            'Connection could not be established with host '.$this->_params['host'].
            ' ['.$errstr.' #'.$errno.']'
            );
    }
    if (!empty($this->_params['blocking'])) {
        stream_set_blocking($this->_stream, 1);
    } else {
        stream_set_blocking($this->_stream, 0);
    }
    stream_set_timeout($this->_stream, $timeout);
    $this->_in = &$this->_stream;
    $this->_out = &$this->_stream;
}
Hope you will solve this problem.....