= dns =
Domain name service


= Check mail record with dig =
 * dig mx bitarus.allowed.org

= Check mail record with dig directly in name server =
 * dig mx bitarus.allowed.org @ns.bitarus.allowed.org

= Check reverse dns  =
 * dig -x 54.68.9.58

= Ask for Reverse DNS for EC2 Elastic IP address =
 * https://portal.aws.amazon.com/gp/aws/html-forms-controller/contactus/ec2-email-limit-rdns-request