localhost and "stream_socket_enable_crypto(): SSL operation failed with code 1"

Editor's note: disabling SSL verification has security implications. Without verification of the authenticity of SSL/HTTPS connections, a malicious attacker can impersonate a trusted endpoint (such as GitHub or some other remote Git host), and you'll be vulnerable to a Man-in-the-Middle Attack. Be sure you fully understand the security issues before using this as a solution.

You should add below code in /config/mail.php ( worked on laravel 5.4 )

'stream' => [
'ssl' => [
    'allow_self_signed' => true,
    'verify_peer' => false,
    'verify_peer_name' => false,
],
],

as you should never change code in vendors as suggested by Sultan Ahmad

That's an error with your SSL certificate. You're trying to use a SSL connection (encrypted, secure connection) without a proper certificate.

That's because you're connecting from localhost, which isn't secure, and that is blocked by the connection. You could avoid that by changing your localhost connection to a SSL based one.

See this link for more details.