Expected response code 250 but got an empty response laravel 8

https://blog.trippyboy.com/2021/laravel/laravel-expected-response-code-250-but-got-an-empty-response/

./config/mail.php

'local_domain' => env('MAIL_HOST'),


'default' => env('MAIL_MAILER', 'smtp'),
'mailers' => [
    'smtp' => [
        'transport' => 'smtp',
        'host' => env('MAIL_HOST', 'smtp.mailgun.org'),
        'port' => env('MAIL_PORT', 587),
        'encryption' => env('MAIL_ENCRYPTION', 'tls'),
        'username' => env('MAIL_USERNAME'),
        'password' => env('MAIL_PASSWORD'),
        'timeout' => null,
        'auth_mode' => null,
        'local_domain' => env('MAIL_HOST'),
],

laravel rules validate multiple row for other column

Multiple parts (id, name, finish, finish_noe)

finish = 2 is Job OK

protected $rules = [
    'parts.*.finish_note' => ['required_if:parts.*.finish,2'],
]