IMAP4 Multi-Accessed Mailbox Practice
RFC 2180
| Document | Type |
RFC - Informational
(July 1997; No errata)
Was draft-gahrns-imap-practice (individual)
|
|
|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | Legacy | ||
| Formats | plain text pdf html bibtex | ||
| Stream | Legacy state | (None) | |
| Consensus Boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | RFC 2180 (Informational) | |
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
Network Working Group M. Gahrns
Request for Comments: 2180 Microsoft
Category: Informational July 1997
IMAP4 Multi-Accessed Mailbox Practice
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
1. Abstract
IMAP4[RFC-2060] is rich client/server protocol that allows a client
to access and manipulate electronic mail messages on a server.
Within the protocol framework, it is possible to have differing
results for particular client/server interactions. If a protocol does
not allow for this, it is often unduly restrictive.
For example, when multiple clients are accessing a mailbox and one
attempts to delete the mailbox, an IMAP4 server may choose to
implement a solution based upon server architectural constraints or
individual preference.
With this flexibility comes greater client responsibility. It is not
sufficient for a client to be written based upon the behavior of a
particular IMAP server. Rather the client must be based upon the
behavior allowed by the protocol.
By documenting common IMAP4 server practice for the case of
simultaneous client access to a mailbox, we hope to ensure the widest
amount of inter-operation between IMAP4 clients and servers.
The behavior described in this document reflects the practice of some
existing servers or behavior that the consensus of the IMAP mailing
list has deemed to be reasonable. The behavior described within this
document is believed to be [RFC-2060] compliant. However, this
document is not meant to define IMAP4 compliance, nor is it an
exhaustive list of valid IMAP4 behavior. [RFC-2060] must always be
consulted to determine IMAP4 compliance, especially for server
behavior not described within this document.
Gahrns Informational [Page 1]
RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
2. Conventions used in this document
In examples,"C1:", "C2:" and "C3:" indicate lines sent by 3 different
clients (client #1, client #2 and client #3) that are connected to a
server. "S1:", "S2:" and "S3:" indicated lines sent by the server to
client #1, client #2 and client #3 respectively.
A shared mailbox, is a mailbox that can be used by multiple users.
A multi-accessed mailbox, is a mailbox that has multiple clients
simultaneously accessing it.
A client is said to have accessed a mailbox after a successful SELECT
or EXAMINE command.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC-2119].
3. Deletion/Renaming of a multi-accessed mailbox
If an external agent or multiple clients are accessing a mailbox,
care must be taken when handling the deletion or renaming of the
mailbox. Following are some strategies an IMAP server may choose to
use when dealing with this situation.
3.1. The server MAY fail the DELETE/RENAME command of a multi-accessed
mailbox
In some cases, this behavior may not be practical. For example, if a
large number of clients are accessing a shared mailbox, the window in
which no clients have the mailbox accessed may be small or non-
existent, effectively rendering the mailbox undeletable or
unrenamable.
Example:
<Client #1 and Client #2 have mailbox FOO accessed. Client #1 tries
to DELETE the mailbox and is refused>
C1: A001 DELETE FOO
S1: A001 NO Mailbox FOO is in use by another user.
Gahrns Informational [Page 2]
RFC 2180 IMAP4 Multi-Accessed Mailbox Practice July 1997
3.2. The server MAY allow the DELETE command of a multi-accessed
mailbox, but keep the information in the mailbox available for
those clients that currently have access to the mailbox.
When all clients have finished accessing the mailbox, it is
permanently removed. For clients that do not already have access to
the mailbox, the 'ghosted' mailbox would not be available. For
example, it would not be returned to these clients in a subsequent
LIST or LSUB command and would not be a valid mailbox argument to any
other IMAP command until the reference count of clients accessing the
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