Internet Message Access Protocol (IMAP) - STATUS=SIZE Extension
Dovecot OyLars Sonckin Kaari 1002600EspooFinlandstephan.bosch@dovecot.fi
ART
EXTRAimapstatussizeThis document adds a new capability called "STATUS=SIZE" to the Internet
Message Access Protocol (IMAP). It allows retrieving the total storage size of a
mailbox with a single STATUS command rather than retrieving and summing the
sizes of all individual messages in that mailbox.
This document extends Internet Message Access Protocol
(IMAP) with a new capability called "STATUS=SIZE".
To determine the total storage size of a mailbox, an IMAP client currently needs
to retrieve all message sizes individually using the FETCH command with the
RFC822.SIZE data item. The "STATUS=SIZE" capability provides a more efficient
means to achieve this. It extends the STATUS command with a new "SIZE" data
item, which indicates the total size of all messages in the target mailbox.
This way, this information can be queried with just one STATUS command. When the
"LIST-STATUS" IMAP capability is also available,
the SIZE data item can be queried for many mailboxes at once using just one LIST
command.This capability is particularly useful for IMAP clients that do not cache the
state of the message store, such as most webmail clients. Without the
"STATUS=SIZE" capability, such clients need to fetch all message sizes from the
server when the size of a mailbox needs to be determined, for example when the
user requests detailed quota usage information. The "QUOTA" capability
is no help in that scenario, since the provided QUOTAROOT
command can only yield the "STORAGE" resource usage of a whole quota root, but
not for a single mailbox within that root.In examples, "C:" indicates lines sent by a client that is connected
to a server. "S:" indicates lines sent by the server to the client.
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 .
This extension defines one new status data item for the STATUS command and
response:
The total size of the mailbox in octets. This MUST be equal to the sum of the
values of the RFC822.SIZE FETCH message data item
of all messages in the mailbox.
Example:The same information can be obtained by using the following commands,
albeit less efficient:When the LIST-STATUS IMAP capability is
also available, the STATUS command can be combined with the LIST command to
further improve efficiency. This way, the sizes of many mailboxes can be
queried with just one LIST command.Example:The following syntax specification augments the grammar specified in
. It uses the Augmented Backus-Naur Form (ABNF)
notation as specified in . Elements not defined here are
taken from .[FIXME: Interaction with 64BIT capability]
There are no known additional security issues with this extension
beyond those described for the base protocol and
for the LIST-STATUS extension .The IANA is requested to add "STATUS=SIZE" to the "IMAP Capabilities"
registry located at
<http://www.iana.org/assignments/imap-capabilities>.Thanks to Bron Gondwana, Alexey Melnikov, Stan Kalisch, and Michael Slusarz
for reviews and suggestions.Key words for use in RFCs to Indicate Requirement LevelsHarvard University1350 Mass. Ave.CambridgeMA 02138- +1 617 495 3864sob@harvard.edu
General
keywordAugmented BNF for Syntax Specifications: ABNFINTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1IMAP4 Extension for Returning STATUS Information in Extended LISTIMAP4 QUOTA extensionCarnegie-Mellon University5000 Forbes Ave.PittsburghPA15213-3890USjgm+@cmu.edu