Hello Robert, Thank you for your reply. It is the way I did it yes, and it works but only inside the same domain:

• setting acl of userA@domA to include userC@domA works well, and appears under the "Shared" pseudo-folder
• but setting acl of userA@domA to include userB@domB does not appear under the "Shared" Here is the config

# 2.2.13: /etc/dovecot/dovecot.conf auth_mechanisms = plain login default_login_user = virmail first_valid_gid = 5501 first_valid_uid = 5501 imap_client_workarounds = delay-newmail tb-extra-mailbox-sep tb-lsub-flags last_valid_gid = 50001 last_valid_uid = 50001 listen = * log_path = /sd/_host-1/var/log/dovecot/dovecot.log log_timestamp = "%Y-%m-%d %H:%M:%S " mail_access_groups = virmail mail_location = maildir:/sd/MAIL_IMAP_POP/%d/%n:LAYOUT=fs mail_plugins = quota notify acl mail_privileged_group = virmail mail_temp_dir = /sd/tmp mailbox_list_index = yes managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave vnd.dovecot.filter namespace { hidden = no list = children location = maildir:/sd/MAIL_IMAP_POP/%d/Public:LAYOUT=fs:CONTROL=/sd/MAIL_IMAP_POP/%d/%n/__Public:INDEX=/sd/MAIL_IMAP_POP/%d/%n/__Public prefix = Public/ separator = / subscriptions = no type = public name = } namespace { list = yes location = maildir:/sd/MAIL_IMAP_POP/%%d/%%n:LAYOUT=fs:INDEX=/sd/MAIL_IMAP_POP/%d/%n/__Shared/%%u:INDEXPVT=/sd/MAIL_IMAP_POP/%d/%n/__Shared/%%u prefix = Shared/%%d/%%n/ separator = / subscriptions = yes type = shared name = } namespace { inbox = yes location = mailbox { auto = subscribe special_use = \Drafts name = Drafts } mailbox { auto = subscribe special_use = \Junk name = Junk } mailbox { special_use = \Sent name = Sent } mailbox { special_use = \Sent name = Sent Messages } mailbox { special_use = \Trash name = Trash } prefix = separator = / type = private name = inbox } passdb { driver = pam } passdb { args = scheme=CRYPT username_format=%u /sd/MAIL_IMAP_POP/%d/passwd_%d driver = passwd-file } passdb { args = scheme=SHA1 /sd/MAIL_IMAP_POP/%d/passwd_%d driver = passwd-file } plugin { acl = vfile:/etc/dovecot/global-acls:cache_secs=300 acl_shared_dict = file:/sd/MAIL_IMAP_POP/%d/shared-mailboxes antispam_backend = pipe antispam_pipe_program = /usr/bin/spamc antispam_pipe_program_args = --username;debian-spamd antispam_pipe_program_notspam_arg = --learntype=ham antispam_pipe_program_spam_arg = --learntype=spam antispam_pipe_tmpdir = /sd/tmp antispam_signature = X-Spam-Flag antispam_signature_missing = move antispam_spam = Spam;Junk antispam_spam_pattern = spam;Spam;junk;Junk antispam_spam_pattern_ignorecase = SPAM;JUNK antispam_trash = trash;Trash;Deleted Items;Deleted Messages antispam_trash_pattern = trash;Trash;Deleted * antispam_trash_pattern_ignorecase = TRASH quota = maildir:User quota:ns= quota2 = maildir:Public quota:ns=Public/ quota2_rule = *:storage=2G quota_exceeded_message = Storage quota for this account has been exceeded, please try again later. quota_rule = *:storage=1G quota_rule2 = Trash:storage=+10%% quota_rule3 = Spam:storage=+20%% quota_status_nouser = DUNNO quota_status_overquota = 552 5.2.2 Mailbox is full quota_status_success = DUNNO quota_warning = storage=90%% quota-warning 90 %u %d quota_warning2 = storage=75%% quota-warning 75 %u %d sieve = /sd/MAIL_IMAP_POP/%d/%n/__Sieve sieve_after = /sd/MAIL_IMAP_POP/%d/SieveAfter/ sieve_after2 = /sd/MAIL_IMAP_POP/SieveAfter/ sieve_before = /sd/MAIL_IMAP_POP/SieveBefore sieve_default = /sd/_host-1/var/lib/dovecot/sieve/default.sieve sieve_extensions = +vnd.dovecot.filter sieve_filter_bin_dir = /etc/dovecot/sieve-filters sieve_global_dir = /sd/_host-1/var/lib/dovecot/sieve/global/ sieve_plugins = sieve_extprograms } postmaster_address = postmaster@domA protocols = imap sieve service replication-notify-fifo { name = aggregator } service anvil-auth-penalty { name = anvil } service auth-worker { user = $default_internal_user name = auth-worker } service { unix_listener { group = postfix mode = 0660 user = postfix path = /var/spool/postfix/private/auth } user = root name = auth } service config { name = config } service dict { name = dict } service login/proxy-notify { name = director } service dns-client { name = dns_client } service doveadm-server { name = doveadm } service { inet_listener { port = 0 name = imap } inet_listener { port = 993 name = imaps } process_min_avail = 1 user = virmail name = imap-login } service imap-urlauth { name = imap-urlauth-login } service imap-urlauth-worker { name = imap-urlauth-worker } service token-login/imap-urlauth { name = imap-urlauth } service login/imap { name = imap } service indexer-worker { name = indexer-worker } service indexer { name = indexer } service ipc { name = ipc } service { unix_listener { group = postfix mode = 0666 user = postfix path = /var/spool/postfix/private/dovecot-lmtp } name = lmtp } service log-errors { name = log } service sieve { name = managesieve-login } service login/sieve { name = managesieve } service pop3 { name = pop3-login } service login/pop3 { name = pop3 } service { executable = script /sd/MAIL_IMAP_POP/_scripts/quota-warning unix_listener { user = virmail path = quota-warning } user = virmail name = quota-warning } service replicator-doveadm { name = replicator } service login/ssl-params { name = ssl-params } service stats-mail { name = stats } ssl_ca =

Thank you for your help

On 01/28/2017 10:40 PM, Robert Schetterer wrote:

...

Hello Community,

I am facing the following question: how is it possible to share malboxes between domains?

Example:

• 2 domains present on the same dovecot: domA and domB
• userA@domA
• userB@domB

userA@domA wants to share his mailbox to userB@domB (again same server)?

Thank you for your help.

Greetz https://wiki2.dovecot.org/ACL

Am 28.01.2017 um 22:22 schrieb dovecot@avv.solutions: this works also cross domain

you may use https://addons.mozilla.org/de/thunderbird/addon/imap-acl-extension/

or horde webmail, roundcube webmail

Best Regards MfG Robert Schetterer