How to deal with self-signed TLS certificates in Laravel's SMTP driver?

I'm trying to send an email with this configuration:

return [

    'driver'     => 'smtp',

    'host'       => 'mail.mydomain.com',

    'port'       => 26,

    'from'       => ['address' => 'mailer@mydomain.com', 'name' => 'Mailer'],

    'encryption' => 'tls',

    'username'   => env('MAIL_USERNAME'),

    'password'   => env('MAIL_PASSWORD'),

    'sendmail'   => '/usr/sbin/sendmail -bs',

    'pretend'    => false,

];

When I submit the form I receive this erorr:

ErrorException in StreamBuffer.php line 95:
stream_socket_enable_crypto(): SSL operation failed with code 1.
OpenSSL Error messages:
error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed

I found this solution where people seems to have solved the problem with the same library but I cant manage to solve it in Laravel.

https://github.com/PHPMailer/PHPMailer/issues/368

Well in that link you provided the solution is straight-forward.

The correct solution is to fix your SSL config - it's not PHP's fault!

how to fix it? in config/mail.php ,'driver' => env('MAIL_DRIVER', 'smtp'), should be 'driver' => env('MAIL_DRIVER', 'mail'), (credits: Danyal Sandeelo)