Which protocol is primarily used for querying DNS?

The primary protocol used for querying the Domain Name System (DNS) is DNS itself. This protocol facilitates the resolution of human-readable domain names into machine-readable IP addresses. When a user types a web address into their browser, for instance, a DNS query is sent out to translate that domain name into an IP address that can be used to locate the desired resource on the internet.

DNS operates mainly over UDP (User Datagram Protocol) due to the need for speed and efficiency in resolving domain names. It can also use TCP (Transmission Control Protocol) for tasks that require a more reliable connection, such as zone transfers. Since DNS is the specific protocol designed for this purpose, it is the clear choice when identifying which protocol facilitates DNS queries.

In contrast, the other protocols mentioned serve completely different purposes. For example, POP3 (Post Office Protocol version 3) and IMAP (Internet Message Access Protocol) are both used for retrieving emails from a server, while SMTP (Simple Mail Transfer Protocol) is primarily used for sending emails. These protocols do not facilitate domain name resolution; hence, they are not relevant to the question at hand.