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

Mailbox Formats

See https://doc.dovecot.org/admin_manual/mailbox_formats/

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.

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

None: MailboxFormat (last edited 2021-05-24 20:29:04 by 2601:281:200:6a:956c:1781:9c63:3873)