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How to create and manage public folder

[TOC]

iRedMail has setting for public folder in /etc/dovecot/dovecot.conf, what you need to do is:

enable the setting for public folder
choose a preferred directory as public folder
set proper ACL rules to control the access

In this tutorial, we will show you how to share a public folder named TestFolder.

Enable public folder in Dovecot

Find sample settings like below in Dovecot config file /etc/dovecot/dovecot.conf:

# Public mailboxes.
# Refer to Dovecot wiki page for more details:
# http://wiki2.dovecot.org/SharedMailboxes/Public
#namespace {
#    type = public
#    separator = /
#    prefix = Public/
#
#    # CONTROL=: Mark this public folder as read-only mailbox
#    # INDEX=: Per-user \Seen flag
#    location = maildir:/var/vmail/public/:CONTROL=~/Maildir/public:INDEX=~/Maildir/public
#
#    # Allow users to subscribe to the public folders.
#    subscriptions = yes
#}

Remove comment marks (#) for above namespace {} block, like below:

# Public mailboxes.
# Refer to Dovecot wiki page for more details:
# http://wiki2.dovecot.org/SharedMailboxes/Public
namespace {
    type = public
    separator = /
    prefix = Public/

    # CONTROL=: Mark this public folder as read-only mailbox
    # INDEX=: Per-user \Seen flag
    location = maildir:/var/vmail/public/:CONTROL=~/Maildir/public:INDEX=~/Maildir/public

    # Allow users to subscribe to the public folders.
    subscriptions = yes
}

If you want to share the public folder to all users hosted on same server, please also remove the comment mark in below line in dovecot.conf:

    acl_anyone = allow

Restarting Dovecot service is required after changed its config file.

Important notes:

With above setting, it uses /var/vmail/public as public folder. You're free to change it to a preferred directory. We use /var/vmail/public/ in this tutorial for example.
Please make sure the public folder is owned by user/group vmail:vmail with permission 0700.

Now let's create required folder and our first shared folder TestFolder.

mkdir -p /var/vmail/public/.TestFolder
chown -R vmail:vmail /var/vmail/public/.TestFolder
chmod -R 0700 /var/vmail/public/.TestFolder

!!! note "Notes"

* There's a dot in folder name while creating it, it's `.TestFolder`, not
  `TestFolder`. All folders with a prefixed dot will be considered as an
  IMAP folder by Dovecot with iRedMail default settings.

* There are no `cur/`, `new/` or `tmp/` directories directly under the
  `/var/mail/public/` folder, because the `Public/` namespace isn't a
  mailbox itself. If you create them manually, it does become a selectable
  mailbox.

With steps above, if you login to webmail (or other IMAP client) as any mail user hosted on same server, there's no visible public folder at all -- this is correct, because no one has permission to access this folder right now.

Manage Access Control with `doveadm`

Before we set any permission, let's check the access control of this public folder first with command doveadm acl get:

doveadm acl get -A "Public/TestFolder"

You can see output like below, no access control at all:

Username ID Global Rights

Below is list of all available permissions. Please check Dovecot web site for more details or update.

!!! note "Permissions"

Permission name (short) | Permission name (full) | Comment
---|---|---
l | lookup | Mailbox is visible in mailbox list. Mailbox can be subscribed to.
r | read | Mailbox can be opened for reading.
w | write | Message flags and keywords can be changed, except `\Seen` and `\Deleted`
s | write-seen | `\Seen` flag can be changed
t | write-deleted | `\Deleted` flag can be changed
i | insert | Messages can be written or copied to the mailbox
p | post | Messages can be posted to the mailbox by LDA, e.g. from Sieve scripts
e | expunge | Messages can be expunged
k | create | Mailboxes can be created (or renamed) directly under this mailbox
x | delete | Mailbox can be deleted
a | admin | Administration rights to the mailbox (currently: ability to change ACLs for mailbox)

With shell command below, we grant some permissions to user postmaster@test.com (again, this user is hosted on same server):

doveadm acl set -A "Public/TestFolder" "user=postmaster@test.com" lookup read write write-seen write-deleted insert delete expunge create

Check the ACl with doveadm again:

# doveadm acl get -A "Public/TestFolder"
Username        ID                       Global Rights
postmaster@a.cn user=postmaster@test.com        create delete expunge insert lookup read write

If you now login to webmail (or other IMAP client) as user postmaster@test.com, you can see a new folder TestFolder.

With shell command below, we grant all users hosted on same server lookup, and read permissions:

doveadm acl set -A "Public/TestFolder" "anyone" lookup read

Check the ACl with doveadm now:

# doveadm acl get -A "Public/TestFolder"
Username        ID                       Global Rights
postmaster@a.cn anyone                          lookup read
postmaster@a.cn user=postmaster@test.com        create delete expunge insert lookup read write

If you login to webmail (or other IMAP client) as any user hosted on same server, you can see a new folder TestFolder.

With shell command below we delete access control for user postmaster@test.com:

doveadm acl delete -A "Public/TestFolder" "user=postmaster@test.com"

For more details about ACL control, please read Dovecot tutorials mentioned in References below.

Troubleshooting

If public folder doesn't work as expected, please turn on debug mode in Dovecot to get debug message. If you don't understand the debug message, you can post them to our online support forum to get help.
It's also a good idea to run doveadm command with -D flag to turn on verbose logging, like below:

doveadm -D acl ...

Use someone's mailbox as public folder

If you want to use someone's mailbox as public folder, here's a simplest way to achieve it.

Let's say you want to share user public@domain.com's mailbox as public folder PublicMailbox, and its maildir path is /var/vmail/vmail1/domain.com/p/u/b/public-20160714100502/Maildir/. What you need to do are:

creating a symbol link to this maildir path like below
set proper ACL with doveadm acl (check steps above)

!!! warning

There's a dot prepended in public mailbox name, it's `public/.PublicMailbox`,
not `public/PublicMailbox`.

ln -s /var/vmail/vmail1/domain.com/p/u/b/public-20160714100502/Maildir /var/vmail/public/.PublicMailbox

References

Dovecot official documents:

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