Public Mailboxes

Public mailboxes are typically mailboxes that are visible to all users or to large user groups. They are created by defining a public namespace, under which all the shared mailboxes are. See SharedMailboxes/Permissions for issues related to filesystem permissions. See Namespaces for details of how namespaces are configured.

For example to create a public Maildir mailboxes, use:

# User's private mail location
mail_location = maildir:~/Maildir

# When creating any namespaces, you must also have a private namespace:
namespace {
  type = private
  separator = /
  prefix =
  #location defaults to mail_location.
  inbox = yes
}

namespace {
  type = public
  separator = /
  prefix = Public/
  location = maildir:/var/mail/public
  subscriptions = no
}

In the above example, you would then create Maildir mailboxes under the /var/mail/public/ directory. For example:

# ls -la /var/mail/public/
drwxr-s--- 1 root mail 0 2007-03-19 03:12 .
drwxrws--- 1 root mail 0 2007-03-19 03:12 .lkml
drwxrws--- 1 root mail 0 2007-03-19 03:12 .bugtraq
-rw-rw---- 1 root mail 0 2007-03-19 03:12 dovecot-shared

Note that there are no cur/, new/ or tmp/ directories directly under the /var/mail/public/, because the Public/ namespace isn't a mailbox itself. (If you create them manually, it does become a selectable mailbox. )

The dovecot-shared file isn't directly used for either lkml or bugtraq mailboxes, but if you create a new public mailbox via Dovecot it's automatically copied there.

Note that Dovecot uses Maildir++ layout by default for folders, where the folder names must begin with a "." or Dovecot will ignore them. You can also optionally use the "fs" layout if you want the directory structure to look like:

/var/mail/public/ (root dir)
/var/mail/public/info/ (maildir folder)
/var/mail/public/company/ (maildir folder)

Per-user \Seen flag (v2.2+)

Since v2.2 the recommended way to enable private flags for shared mailboxes is to create private indexes with :INDEXPVT=<path>. This creates dovecot.index.pvt[.log] files, which contain only the message UIDs and the private flags. Currently the list of private flags is hardcoded only to the \Seen flag.

Example:

namespace {
  type = public
  separator = /
  prefix = Public/
  location = maildir:/var/mail/public:INDEXPVT=~/Maildir/public
  subscriptions = no
}

Maildir: Per-user \Seen flag

(With v2.2+ you should instead use the INDEXPVT as described above.)

With Maildir a dovecot-shared file controls if the \Seen flags are shared or private. The file must be created separately inside each Maildir, although if the file already exists in the Maildir root it's automatically copied for newly created mailboxes. If dovecot-shared file doesn't exist in Maildir, the \Seen flags are shared. If it exists, the \Seen flag state is stored only in the user's index files. By making each user have their own private index files, you can make the \Seen flag private for the users. For example:

namespace {
  type = public
  separator = /
  prefix = Public/
  location = maildir:/var/mail/public:INDEX=~/Maildir/public
  subscriptions = no
}

Now when accessing e.g. "Public/lkml" mailbox, Dovecot keeps its index files in ~/Maildir/public/.lkml/ directory. If it ever gets deleted, the \Seen flags are lost.

If you want to change what flags are shared when dovecot-shared file exists, currently you'll have to modify the source code: src/lib-storage/index/maildir/maildir-storage.c maildir_open() has mbox->ibox.box.private_flags_mask = MAIL_SEEN; Change the MAIL_SEEN to any flag combination you want. See src/lib-mail/mail-types.h for list of valid flags.

Maildir: Keyword sharing

Make sure you don't try to use per-user CONTROL directory. Otherwise dovecot-keywords file doesn't get shared and keyword mapping breaks.

Subscriptions

Typically you want each user to have control over their own subscriptions for mailboxes in public namespaces. This is why you should set subscriptions=no to the namespace. Dovecot will then use the parent namespace's subscriptions file. Note that this practically means you must have a namespace with empty prefix, otherwise there is no "parent namespace".

Read-only mailboxes

Read-only mboxes

If you have a read-only directory structure containing mbox files, you'll need to store index files elsewhere:

namespace {
  type = public
  prefix = Public/
  location = mbox:/var/mail/public/:INDEX=/var/indexes/public
  subscriptions = no
}

In the above example all the users would still be sharing the index files, so you might have problems with filesystem permissions. Alternatively you could place the index files under user's home directory.

Read-only Maildirs

If your Maildir is read-only, the control and index files still need to be created somewhere. You can specify the path for these by appending :CONTROL=<path>:INDEX=<path> to mail location. The path may point to a directory that is shared among all users, or to a per-user path. Note that if the Maildir has any keywords, the per-user control directory breaks the keywords since there is no dovecot-keywords file.

When configuring multiple namespaces, the CONTROL/INDEX path must be different for each namespace. Otherwise if namespaces have identically named mailboxes their control/index directories will conflict and cause all kinds of problems.

If you put the control files to a per-user directory, you must also put the index files to a per-user directory, otherwise you'll get errors. It is however possible to use shared control files but per-user index files, assuming you've set up permissions properly.

namespace {
  type = public
  separator = /
  prefix = Public/
  location = maildir:/var/mail/public:CONTROL=~/Maildir/public:INDEX=~/Maildir/public
  subscriptions = no
}
namespace {
  type = public
  separator = /
  prefix = Team/
  location = maildir:/var/mail/team:CONTROL=~/Maildir/team:INDEX=~/Maildir/team
  subscriptions = no
}

Example: Public mailboxes with ACLs

See ACL for more information about ACLs.

namespace {
  type = public
  separator = .
  prefix = public.
  location = maildir:/var/mail/public
  subscriptions = no
  list = children
}

plugin {
  acl = vfile
}

It's important that the namespace type is "public" regardless of whether you set the namespace prefix to "shared." or something else.

After this you have to place dovecot-acl files in every mailbox/folder below /var/mail/public with rights for that folder (e.g. user=someone lr).

acl_shared_dict setting is not relevant for public mailboxes (only for shared).