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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)
                9  TCP/IP Electronic Mail System: Concepts and Protocols (RFC 822, MIME, SMTP, POP3, IMAP)
                     9  TCP/IP Electronic Mail Access and Retrieval Protocols and Methods
                          9  TCP/IP Post Office Protocol (POP/POP3)

Previous Topic/Section
POP3 Authorization State: User Authentication Process and Commands
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POP3 Update State: Mailbox Update and Session Termination Process and Commands
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POP3 Transaction State: Mail and Information Exchange Process and Commands
(Page 1 of 2)

Once the POP3 client has successfully authenticated the user who is performing mailbox access, the session transitions from the Authorization state to the Transaction state. There's no real mystery what this phase of the connection is all about: it is where the POP3 client issues the commands that perform mailbox access and message retrieval transactions.

POP3 Transaction Commands

Most of the commands defined in POP3 are valid only in the Transaction state. Table 257 lists each of them, in the order in which they appear in RFC 1939.


Table 257: POP3 Transaction Commands

Command Code

Command

Parameters

Description

STAT

Status

None

Requests status information for the mailbox. The server will normally respond telling the client the number of messages in the mailbox, and the number of bytes of data it contains. Optionally, more information may also be returned.

LIST

List Messages

Optional message number

Lists information for the messages in a mailbox; generally this means showing the message number and its size. If a message number is given, only that message's information is provided; otherwise, the full contents of the mailbox are described, one line at a time, with a line containing just a single period at the end.

RETR

Retrieve

Message number

Retrieves a particular message from the mailbox. The server responds with a standard “+OK” message and then immediately sends the message in RFC 822 format, one line at a time. A line with a period by itself is sent after the last line.

DELE

Delete

Message number

Marks a message as deleted. Once deleted, any further attempt to access a message (using LIST or RETR for example) results in an error.

NOOP

No Operation

None

Does nothing; the server just returns a +OK reply.

RSET

Reset

None

Resets the session to the state it was in upon entry to the Transaction state. This includes “undeleting” any messages already marked for deletion.

TOP

Retrieve Message Top

Message number and number of lines

Allows a client to retrieve only the beginning of a message. The server returns the headers of the message and only the first N lines where N is the number of lines specified.

This command is optional and may not be supported by all servers.

UIDL

Unique ID Listing

Optional message number

If a message number was specified, returns a unique identification code for that message; otherwise, returns an identification code for each message in the mailbox.

This command is optional and may not be supported by all servers.


Previous Topic/Section
POP3 Authorization State: User Authentication Process and Commands
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2
Next Page
POP3 Update State: Mailbox Update and Session Termination Process and Commands
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Version 3.0 - Version Date: September 20, 2005

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