Suggest an editImprove this articleRefine the answer for “What is SMTP?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)**SMTP (Simple Mail Transfer Protocol)** is an application-layer protocol used to send email. It handles passing messages from the sender to a mail server and between servers. **Key point:** SMTP only handles sending - you cannot receive a message via SMTP, that is what POP3 and IMAP are for.Shown above the full answer for quick recall.Answer (EN)Image**SMTP (Simple Mail Transfer Protocol)** is an **application-layer protocol** used to **send email**. In short: **SMTP is responsible for sending messages from the sender to a mail server and between servers**. --- ## Why SMTP is needed SMTP is needed so that: - a mail client can **send a message** - mail servers can **pass a message to each other** - the message reaches the recipient's server Important: **SMTP is only about sending**, not about reading messages. --- ## How SMTP works (simplified) The process looks like this: 1. The user clicks "Send message" 2. The mail client sends the message via SMTP to its own mail server 3. The sender's mail server finds the recipient's server 4. The servers **pass the message to each other via SMTP** 5. The message arrives at the recipient's server After that, the recipient **retrieves the message using a different protocol**. --- ## SMTP and receiving mail This is a common point of confusion in interviews. - **SMTP** - sending messages - **POP3 / IMAP** - receiving messages You cannot receive a message via SMTP - only send one. --- ## What data SMTP transfers SMTP transfers: - the sender's address - the recipient's address - the subject line - the message body - attachments (in a special format) For SMTP, a message is a **text message with formatting rules**. --- ## SMTP security In its classic form, SMTP: - **does not encrypt data** - transfers logins and messages as plain text So in practice people use: - **SMTP + TLS (STARTTLS)** - protected ports --- ## A real-life example SMTP is like a postal service: - you put a letter in the mailbox - the post delivers it to the right branch - then the recipient picks up the letter themselvesFor the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.