RFC 1939 / START HERE
POP3 mail retrieval, before the details
POP3: Post Office Protocol version 3
POP3 lets a mail client retrieve messages from a server mailbox. Its model is simpler than IMAP's server-side mailbox management.
The idea in one picture
Mail waits on a server
A client retrieves messages
The client manages downloaded copies
A simplified picture of the idea; the chapters explain the actual mechanisms.
Why it exists
A client needs a standard way to collect delivered mail. POP3 focuses on retrieving messages rather than synchronizing a rich folder model.
A familiar example
A desktop mail app downloads messages from a mailbox, with deletion or retention determined by its commands and settings.
Helpful background
You can start here without reading another RFC. If these ideas are unfamiliar, these short introductions may help.
What you’ll learn next
Begin with chapter one, or choose a topic.
- POP3 session statesA POP3 session advances through authorization, transaction, and update.→
- List and retrieve messagesSTAT and LIST describe the maildrop; RETR returns one message.→
- Stable identifiers with UIDLUIDL supports recognizing messages across sessions without relying on temporary message numbers.→
- Deletion and UPDATEDELE marks a message; QUIT from the transaction requests actual deletion processing.→
- Authentication and transport limitsThis historical specification includes authentication mechanisms that do not provide modern transport confidentiality.→
This introduction explains RFC 1939 (1996). Read the original RFC ↗