POP3 Explained: How It Works and What to Look For
POP3 retrieves messages from a mail server.
Published by Protocol Explorer · Reviewed
How POP3 works
A client connects, authenticates, lists or retrieves messages and ends the session. Server responses indicate success or failure of commands.
What to look for in an exchange
Commands such as LIST, RETR and DELE have different effects. Deletion is finalized when the session reaches its update state, subject to server behaviour.
Follow an example step by step
- Follow the server greeting and client authentication state.
- Use LIST and RETR in the example to distinguish message discovery from retrieval.
- If DELE appears, follow the session through QUIT to understand when deletion is committed.
Common interpretation mistake
POP3 is a mailbox retrieval protocol, not the SMTP protocol used to transfer outgoing email.
Key point to remember
TLS deployment and server policies determine how credentials and message contents are protected in transit.
Explore the protocol
The POP3 overview is free without an account. Its full interactive lesson is included in Protocol Explorer Pro, a one-time $4.99 purchase; an account is required to buy Pro and restore the licence across devices.
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Specification
Read the primary specification for POP3 for the authoritative protocol details. The interactive scenario is a simplified teaching model, not a capture of your network.
Continue learning
How to read a packet · TCP · UDP · HTTPS