Which protocol is commonly used for sending emails?

The protocol that is commonly used for sending emails is Simple Mail Transfer Protocol (SMTP). SMTP is specifically designed for the transmission of email messages between servers. It facilitates the process of sending messages from the sender's email server to the recipient's email server and allows for the routing of emails over the internet.

SMTP operates mainly over the TCP/IP protocol suite, making it integral to email communication. It establishes a set of rules governing how email messages are sent, ensuring they are delivered correctly and efficiently. This protocol defines the format for email messages and controls the transfer of messages from the client to the server and between the servers themselves.

In contrast, the other protocols mentioned serve different purposes. HTTP (Hypertext Transfer Protocol) is used for transferring hypertext requests and information on the web. FTP (File Transfer Protocol) is used for transferring files between computers. DNS (Domain Name System) translates domain names into IP addresses, enabling browsers to locate web resources. Each of these protocols is crucial for their specific functions, but none are designed for email transmission like SMTP is.