Expected response code 250 but got code “530”, with message “530 5.7.1 Authentication required

your mail.php on config you declare host as smtp.mailgun.org and port is 587 while on env is different. you need to change your mail.php to

'host' => env('MAIL_HOST', 'mailtrap.io'),

'port' => env('MAIL_PORT', 2525),

if you desire to use mailtrap.Then run

php artisan config:cache