What protocol is used to send email?

SMTP, the Simple Mail Transfer Protocol, is used to send email between mail systems and from an email client to an outgoing mail server.

SMTP is an Internet standard for transferring electronic mail. When you press Send, your email program typically submits the message to a mail server using SMTP. That server then uses SMTP to relay the message toward the recipient’s mail server, where it is eventually stored for retrieval.

SMTP is primarily an outgoing-mail protocol, which is why it is commonly associated with sending rather than reading messages. IMAP and POP3 serve different roles: IMAP synchronizes messages stored on a mail server, while POP3 generally downloads messages to a device. HTTP is designed for web communication, not ordinary email delivery.

Modern email submission commonly uses port 587 with authentication, while encrypted SMTP connections may use port 465. SMTP itself does not guarantee that a message is genuine or private; systems use additional technologies such as TLS, SPF, DKIM, and DMARC to improve transport security and combat spoofing.