mail_location setting in dovecot.conf is used if nothing else overrides it.
(User Databases(SQL)  <overrides  namespaces)

Default: ~/Maildir

mail_location  = mailbox-format : path [ : key = value … ]

key:
INDEX : specifies the location of index files.
(disable the index files completely by appending :INDEX=MEMORY. )
SUBSCRIPTIONS : specifies the file used for storing subscriptions.(subscriptions)
DIRNAME : specifies the directory name used for mailbox directories(dbox-Mails/)

userdb

If you're using a single UID and GID for all users, you can set them in dovecot.conf with:
(static userdb)

userdb {
  driver = static
  args = uid=500 gid=500 home=/home/%u
}

or

mail_uid = vmail
mail_gid = vmail

dovecot-sql.conf file:

CREATE TABLE users (
    userid VARCHAR(128) NOT NULL,
    domain VARCHAR(128) NOT NULL,
    password VARCHAR(64) NOT NULL,
    home VARCHAR(255) NOT NULL,
    uid INTEGER NOT NULL,
    gid INTEGER NOT NULL
);

conf

driver = sqlite

connect = /path/to/sqlite.db

password_query = SELECT userid AS username, domain, password \
  FROM users WHERE userid = '%n' AND domain = '%d'
user_query = SELECT home, uid, gid FROM users WHERE userid = '%n' AND domain = '%d'

# For using doveadm -A:

iterate_query = SELECT userid AS username, domain FROM users

dbox

dbox is Dovecot's own high-performance mailbox format.

reasons for dbox's high performance

it uses Dovecot's index files as the storage for message flags and keywords,

so the indexes don't have to be "synchronized" (Index files actually contain significant data)

This data cannot be automatically recreated, so it is important that Index files are treated with the same care as message data files.

一共有兩種 dbox

• single-dbox (sdbox in mail location): One message per file, similar to Maildir.
• multi-dbox (mdbox in mail location): Multiple messages per file

 * Unlike Maildir, with dbox the message file names don't change.

Config

# mail_location = maildir:~/Maildir      # Maildir
mail_location = sdbox:~/sdbox             # single-dbox

maildir -> dbox migration

Set

mail_location=sdbox:~/sdbox

and run

dsync -u username mirror maildir:~/Maildir

dsync

SYNOPSIS

       dsync [options] mirror location2

       dsync [options] backup location2

  mirror

       Does a two-way synchronization between two mail locations.  Changes  in
       both  locations  are  synchronized to the other one, without losing any
       changes made by either  of  them.   Any  potential  UID  conflicts  are
       resolved by giving them new UIDs.

   backup

       Backup mails from default mail location to location2 (or vice versa, if
       -R parameter is given).   No  changes  are  ever  done  to  the  source
       location.  Any changes done in destination are discarded.

Two-way synchronization of mailboxes in different servers (via ssh)
(dsync will merge the changes without losing any changes done on either side.)
(Dovecot's index logs that keep track of changes.)

好處:

creating backups of mails to a remote server

dsync can be run completely standalone.

opts:

-u    parameter to do a userdb lookup from auth process.

-v    Makes dsync more verbose.

-R    Reverse backup direction, so mails in location2 are backed up to default mail location.

i.e.

dsync -u username mirror ssh -i id_dsa.dovecot [email protected] dsync -u username