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The TCP/IP Guide

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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 Internet Message Access Protocol (IMAP/IMAP4)

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IMAP Not Authenticated State: User Authentication Process and Commands
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IMAP Selected State: Message Manipulation Process and Commands
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IMAP Authenticated State: Mailbox Manipulation/Selection Process and Commands
(Page 1 of 2)

In the normal progression of an IMAP session, the Authenticated state is the first one where the IMAP client is able to perform “useful work” on behalf of its user. This state will normally be reached from the Not Authenticated state after successful authentication using the LOGIN or AUTHENTICATE command. Alternately, a server may preauthenticate a client and begin the session in this state directly.

Once in the Authenticated state, the client is considered authorized to issue commands to the server. However, it may only give commands that deal with whole mailboxes. As mentioned in the general operation overview, IMAP was created to allow access to, and manipulation of, multiple mailboxes. For this reason, the client must specify dynamically which mailbox it wants to use before commands dealing with individual messages may be given. This is done in this state using the SELECT or EXAMINE commands, which cause a transition to the Selected state as we will see.

It is also possible that the Authenticated state can be re-entered during the course of a session. If the CLOSE command is used from the Selected state to close a particular mailbox, the server will consider that mailbox “de-selected” and the session will transition back to the Authenticated state until a new selection is made. The same can occur if a new SELECT or EXAMINE command is given from the Selected state but fails.

Authenticated State Commands

Table 261 provides a brief description of the mailbox-manipulation commands that can be used in the Authenticated state:

Table 261: IMAP Authenticated State Commands





Mailbox name

Selects a particular mailbox so that messages within it can be accessed. If the command is successful, the session transitions to the Selected state. The server will also normally respond with information for the client about the selected mailbox; see below.


Mailbox name

Exactly the same as the SELECT command, except that the mailbox is opened “read-only”; no changes are allowed to it.


Mailbox name

Creates a mailbox with the given name.


Mailbox name

Deletes the specified mailbox.


Current and new mailbox names

Renames a mailbox.


Mailbox name

Adds the mailbox to the server's set of “active” mailboxes. This is sometimes used when IMAP4 is employed for Usenet message access.


Mailbox name

Removes the mailbox from the “active” list.


Mailbox name or reference string

Requests a partial list of available mailbox names, based on the parameter provided.


Mailbox name or reference string

The same as LIST but only returns names from the “active” list.


Mailbox name

Requests the status of the specified mailbox. The server responds providing information such as the number of messages in the box and the number of recently-arrived and unseen messages.


Mailbox name, message, optional flags and date/time

Adds a message to a mailbox.

Note: All of the commands above may also be used in the Selected state; they should really be called “Authenticated+Selected” state.commands.

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Version 3.0 - Version Date: September 20, 2005

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