This documentation is for Dovecot v2.x, see wiki1 for v1.x documentation.

Mailbox Formats

Mailbox formats supported by Dovecot:

Name

Tag

Description

mbox

mbox

Traditional UNIX mailbox format. Users' INBOX mboxes are commonly stored in /var/spool/mail or /var/mail directory. Single file contains multiple messages.

Maildir

maildir

One file contains one message. A reliable choice since files are never modified and all operations are atomic. The top-level Maildir directory contains the Maildir/cur, Maildir/new and Maildir/tmp subdirectories.

dbox

sdbox

single-dbox, one message per file

Dovecot's own high performance mailbox format. Messages are stored in one or more files, each containing one or more messages.

mdbox

multi-dbox, multiple messages per file

dbox

deprecated alias for sdbox

Cydir

cydir

Dovecot's own simple and high performance Cyrus-like mailbox format. It should be mostly used for testing and benchmarking only.

The Tag column indicates the tag which is used at the beginning of a mailbox location specification.

Mailbox formats not supported by Dovecot:

Name

Description

mbx

UW-IMAP's old high performance mailbox format. One file contains all the mailboxes, so expunges may still be slow.

mix

UW-IMAP's new (2006) high performance mailbox format. Similar to multi-dbox.

mailstore

A format created by Exim.

MH

One file contains one message. Sort order of the folder determines the message ID and name. Actively used by projects such as MH-E, NMH, exmh. Experimentally supported by UW-IMAP.

MMDF

Similar to mbox, but instead of From-line separators it uses four ^A characters

Cyrus

One file contains one message, plus there are a couple of index/cache files. Commonly referred to as being maildir-like, although they have only a single thing in common.

Adding support for new formats for Dovecot isn't very difficult, although it can be time consuming. Dovecot exposes a nice and simple API which needs to be implemented. Use Cydir format as an example.

Software Support

Format/Software

Dovecot

UW-IMAP

Courier-IMAP

Exim

Postfix

PINE

mutt

procmail

maildrop

mbox

Yes

Yes

No

Yes

Yes

Yes

Yes

Yes

Yes

mbx

No

Yes

No

Yes

No

Yes

No

No

No

maildir

Yes

No

Yes

Yes

Yes

No

Yes

Yes (3.22)

Yes

mailstore

No

No

No

Yes

No

No

No

No

No

dbox

Yes

No

No

No

No

No

No

No

No

MH

No

Yes

No

No

No

Yes

Yes

Yes

No

Conversion Between Mailbox Formats

See Migration/MailFormat.

References

MailboxFormat (last edited 2010-09-03 13:38:41 by TimoSirainen)