I had this issue too, this is how i fixed it. Though it is not advisable to change vendor files but this fix worked and it enable me to send mail from my localhost.
C:\xampp\htdocs\mylaravel\vendor\swiftmailer\swiftmailer\lib\classes\Swift\Transport
$options[‘ssl’][‘verify_peer’] = FALSE;
$options[‘ssl’][‘verify_peer_name’] = FALSE;
private function _establishSocketConnection(){
....
$options['ssl']['verify_peer'] = FALSE;
$options['ssl']['verify_peer_name'] = FALSE;
$streamContext = stream_context_create($options);
$this->_stream = @stream_socket_client($host.':'.$this->_params['port'],
$errno, $errstr, $timeout, STREAM_CLIENT_CONNECT, $streamContext);
.... }
It’s like the ssl keeps preventing the mail from been sent. I hope this helps