mengirim email dengan akun email hosting sendiri di laravel

kenapa saya saat mengirim email selalu gagal?

errornya : Connection could not be established with host mail.mydomain.com [php_network_getaddresses: getaddrinfo failed: No such host is known. #0]

MAIL_DRIVER=smtp
MAIL_HOST=mail.mydomain.com
MAIL_PORT=port.port.net (udah sesuai)
MAIL_USERNAME=info@mydomain.com
MAIL_PASSWORD=mydomainpassword
MAIL_ENCRYPTION=null