Solution : Domain name system is used to determine the IP address of the host/domain name. DNS is very useful to every user where it helps retrieve the website IP address. Without DNS we cannot retrieve the website IP address. This process is known as forward DNS resolution. DNS should be registered by some companies. If any attacker has details then the dns will be controlled by the attacker. when we are sending the e-mail the dns data will be used then it can be catches anywhere in the network. So it is very important that a DNS require reliable communications..