Connection Could not be established with host smtp.gmail.com - Laravel

I'm trying to send email by using gmail(personal email address) but failed as below error. there is no error when I using a public network to send the email but failed when I using office network that comes with firewall setting.

I have tried the method to set the the mail_mailer to "sendmail" but still failed. Really appreciate if someone can help on this.

Below is my code in .env and also mail.php

code in .env

APP_NAME=KPI
APP_ENV=local
APP_KEY=base64:0SydcKbNLuXKE5PQgxlHIDWS/EGi8Sle2SrN2R+AGUo=
APP_DEBUG=true
APP_URL=http://localhost

LOG_CHANNEL=stack
LOG_LEVEL=debug

DB_CONNECTION=mysql
DB_HOST=127.0.0.1
DB_PORT=3306
DB_DATABASE=kpi
DB_USERNAME=root
DB_PASSWORD=

BROADCAST_DRIVER=log
CACHE_DRIVER=file
QUEUE_CONNECTION=sync
SESSION_DRIVER=file
SESSION_LIFETIME=120

MEMCACHED_HOST=127.0.0.1

REDIS_HOST=127.0.0.1
REDIS_PASSWORD=null
REDIS_PORT=6379

MAIL_DRIVER=smtp
MAIL_HOST=smtp.gmail.com
MAIL_PORT=587
MAIL_USERNAME=example@gmail.com
MAIL_PASSWORD=example12345
MAIL_ENCRYPTION=tsl
MAIL_FROM_ADDRESS=example@gmail.com
MAIL_FROM_NAME="${APP_NAME}"

AWS_ACCESS_KEY_ID=
AWS_SECRET_ACCESS_KEY=
AWS_DEFAULT_REGION=us-east-1
AWS_BUCKET=

PUSHER_APP_ID=
PUSHER_APP_KEY=
PUSHER_APP_SECRET=
PUSHER_APP_CLUSTER=mt1

MIX_PUSHER_APP_KEY="${PUSHER_APP_KEY}"
MIX_PUSHER_APP_CLUSTER="${PUSHER_APP_CLUSTER}"

code in mail.php

<?php

return [

    'default' => env('MAIL_DRIVER', 'smtp'),

    'mailers' => [
        'smtp' => [
            'transport' => 'smtp',
            'host' => env('MAIL_HOST', 'smtp.mailgun.org'),
            'port' => env('MAIL_PORT', 465),
            'encryption' => env('MAIL_ENCRYPTION', 'tsl'),
            'username' => env('MAIL_USERNAME'),
            'password' => env('MAIL_PASSWORD'),
            'timeout' => null,
            'auth_mode' => null,
        ],

        'ses' => [
            'transport' => 'ses',
        ],

        'mailgun' => [
            'transport' => 'mailgun',
        ],

        'postmark' => [
            'transport' => 'postmark',
        ],

        'sendmail' => [
            'transport' => 'sendmail',
            'path' => '/usr/sbin/sendmail -bs',
        ],

        'log' => [
            'transport' => 'log',
            'channel' => env('MAIL_LOG_CHANNEL'),
        ],

        'array' => [
            'transport' => 'array',
        ],
    ],

   

    'from' => [
        'address' => env('MAIL_FROM_ADDRESS', 'hello@example.com'),
        'name' => env('MAIL_FROM_NAME', 'Example'),
    ],
    
    'stream' => [
        'ssl' => [
            'allow_self_signed' => true,
            'verify_peer' => false,
            'verify_peer_name' => false,
        ],
    ],


    'markdown' => [
        'theme' => 'default',

        'paths' => [
            resource_path('views/vendor/mail'),
        ],
    ],

];

via Chebli Mohamed