Here's my setting for mail gun.
in my .env file. mail settings
MAIL_DRIVER= mailgun
MAILGUN_DOMAIN = sandbox........mailgun.org
MAIL_HOST = smtp.mailgun.org
MAIL_PORT =587
MAIL_USERNAME = postmaster@sandbox..........mailgun.org
MAIL_PASSWORD = 0maigunpassword
MAILGUN_SECRET = key-...........
MAIL_FROM = ticket@sandbox..........mailgun.org
MAIL_ENCRYPTION=tls
in my services.php
'mailgun' => [
'domain' => env('MAILGUN_DOMAIN'),
'secret' => env('MAILGUN_SECRET'),
],