What protocol sends emails?

SMTP, which stands for Simple Mail Transfer Protocol, is the industry-standard protocol used for sending and receiving email messages across the internet. It defines the rules and procedures for how email servers communicate with each other to deliver mail from a sender to a recipient. When you send an email, your email client typically uses SMTP to send the message to your outgoing mail server, which then uses SMTP to relay it to the recipient's mail server. Other options like HTTP (Hypertext Transfer Protocol) are used for web browsing, FTP (File Transfer Protocol) for transferring files between computers, and TCP/IP (Transmission Control Protocol/Internet Protocol) is a foundational suite of protocols that governs how data is exchanged over the internet, not specifically for email sending.