email send smtp error on direct admin server

Question

I am using Directadmin as hosting for my cakephp website. I have used gmail SMTP to send mail.

'EmailTransport' => [
    'default' => [
        'host' => 'localhost',
        'port' => 25,
        'username' => null,
        'password' => null,
        'client' => null,
        'url' => env('EMAIL_TRANSPORT_DEFAULT_URL', null),
    ],
    'gmail' => [
        'host' => 'smtp.gmail.com',
        'port' => 587,
        'username' => '[email protected]', //eg: sample[at]gmail.com
        'password' => 'dummypassword', //email password
        'className' => 'Smtp',
        'tls' => true,
        'client' => null,
        'url' => env('EMAIL_TRANSPORT_DEFAULT_URL', null),
    ],
],

The code is running properly on localhost but it is showing the following error on server

stream_socket_client(): Unable to connect to tcp://smtp.gmail.com:587 (Network is unreachable) please help with the solution