SMTP
SMTP stands for Simple Mail Transfer Protocol.
It is the standard protocol used to send emails between mail servers or from a mail client to a server. SMTP defines how email messages are formatted, transferred, and relayed across networks.
🔌 What SMTP Does (and Doesn’t Do)
| SMTP does | SMTP does not |
|---|---|
| Send email from client to server | Retrieve emails from mailbox |
| Send email server to server | Store emails long-term |
| Relay or forward email | Download messages to your device |
🔧 Common SMTP Ports
| Port | Usage |
|---|---|
| 25 | Server-to-server mail (original SMTP) |
| 587 | Client-to-server (modern standard) ✅ |
| 465 | SMTP over SSL (deprecated, still used) |
🤔 Bonus: What a Typical SMTP Exchange Looks Like
text
HELO client.example.com
MAIL FROM:<you@example.com>
RCPT TO:<friend@example.net>
DATA
Subject: Test
Hello World.
.
QUITThis is the raw SMTP conversation between mail servers or clients.
✅ TL;DR
| SMTP stands for | Simple Mail Transfer Protocol |
|---|---|
| Used for | Sending email from client to server or between servers |
| Defined by | RFC 5321 and related standards |
| Works with | DNS (MX records), optional with TLS, SPF, DKIM, DMARC |