This key facts covers SMTP - Simple Mail Transfer Protocol within Protocols for GCSE Computer Science. Revise Protocols in Networks for GCSE Computer Science with 15 exam-style questions and 18 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 6 of 10 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 6 of 10
Practice
15 questions
Recall
18 flashcards
SMTP - Simple Mail Transfer Protocol
What is SMTP?
Protocol for sending email from client to server, or between email servers. When you click "Send" in your email app, SMTP delivers your message.
How SMTP Works:
- Sending only: SMTP is for SENDING emails, not receiving
- Port 25: Default SMTP port (also 587 for submission)
- Server-to-server: Your mail server forwards message to recipient's mail server
- Store-and-forward: If recipient server is unavailable, SMTP retries later
- Text-based: Uses simple text commands (HELO, MAIL FROM, RCPT TO, DATA)
Email Sending Process:
1. You write email and click Send
2. Your email client uses SMTP to send to your mail server
3. Your mail server uses SMTP to forward to recipient's mail server
4. Recipient's mail server stores the email
5. Recipient uses POP3/IMAP to download email
Receiving Email (POP3/IMAP):
- POP3 (Post Office Protocol): Downloads emails from server to device, then deletes from server
- IMAP (Internet Message Access Protocol): Keeps emails on server, syncs across multiple devices
- SMTP vs POP3/IMAP: SMTP = sending, POP3/IMAP = receiving
SMTP Ports:
- Port 25: Traditional SMTP (server-to-server)
- Port 587: SMTP submission (client-to-server, preferred for modern email)
- Port 465: SMTPS (SMTP over SSL, legacy encrypted version)