IMAP4 Namespace
RFC 2342

Document Type RFC - Proposed Standard (May 1998; No errata)
Updated by RFC 4466
Last updated 2013-03-02
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Network Working Group                                         M. Gahrns
Request for Comments: 2342                                    Microsoft
Category: Standards Track                                     C. Newman
                                                               May 1998

                            IMAP4 Namespace

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

1. Abstract

   IMAP4 [RFC-2060] does not define a default server namespace. As a
   result, two common namespace models have evolved:

   The "Personal Mailbox" model, in which the default namespace that is
   presented consists of only the user's personal mailboxes. To access
   shared mailboxes, the user must use an escape mechanism to reach
   another namespace.

   The "Complete Hierarchy" model, in which the default namespace that
   is presented includes the user's personal mailboxes along with any
   other mailboxes they have access to.

   These two models, create difficulties for certain client operations.
   This document defines a NAMESPACE command that allows a client to
   discover the prefixes of namespaces used by a server for personal
   mailboxes, other users' mailboxes, and shared mailboxes.  This allows
   a client to avoid much of the manual user configuration that is now
   necessary when mixing and matching IMAP4 clients and servers.

2. Conventions used in this document

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.  If such lines are wrapped without a new "C:" or
   "S:" label, then the wrapping is for editorial clarity and is not
   part of the command.

Gahrns & Newman             Standards Track                     [Page 1]
RFC 2342                    IMAP4 Namespace                     May 1998

   Personal Namespace: A namespace that the server considers within the
   personal scope of the authenticated user on a particular connection.
   Typically, only the authenticated user has access to mailboxes in
   their Personal Namespace. It is the part of the namespace that
   belongs to the user that is allocated for mailboxes. If an INBOX
   exists for a user, it MUST appear within the user's personal
   namespace.  In the typical case, there SHOULD be only one Personal
   Namespace on a server.

   Other Users' Namespace: A namespace that consists of mailboxes from
   the Personal Namespaces of other users.  To access mailboxes in the
   Other Users' Namespace, the currently authenticated user MUST be
   explicitly granted access rights.  For example, it is common for a
   manager to grant to their secretary access rights to their mailbox.
   In the typical case, there SHOULD be only one Other Users' Namespace
   on a server.

   Shared Namespace: A namespace that consists of mailboxes that are
   intended to be shared amongst users and do not exist within a user's
   Personal Namespace.

   The namespaces a server uses MAY differ on a per-user basis.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC-2119].

3. Introduction and Overview

   Clients often attempt to create mailboxes for such purposes as
   maintaining a record of sent messages (e.g. "Sent Mail") or
   temporarily saving messages being composed (e.g. "Drafts").  For
   these clients to inter-operate correctly with the variety of IMAP4
   servers available, the user must enter the prefix of the Personal
   Namespace used by the server.  Using the NAMESPACE command, a client
   is able to automatically discover this prefix without manual user

   In addition, users are often required to manually enter the prefixes
   of various namespaces in order to view the mailboxes located there.
   For example, they might be required to enter the prefix of #shared to
   view the shared mailboxes namespace. The NAMESPACE command allows a
   client to automatically discover the namespaces that are available on
   a server. This allows a client to present the available namespaces to
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