Hello, My bad, the OS was ubuntu 20.04 and not 22.04 . After further tinkering\testing, it seems that removing the " acl_ignore_namespace = shared/* " setting did the trick, now we're getting the correct ACL on client side . Without it we can see the folder with the right permissions : Logging as user01 : shared\Sharer01\INBOX : '[NONEXISTENT] Mailbox doesn't exist: shared/test.imapsharer01 at td01.testdomain.it/INBOX'' shared\Sharer01\subfolder01 ( RW ) : 'shared/test.imapsharer01 at td01.testdomain.it/subfolder01 test.imapuser01 at td01.testdomain.it akxeilprwtscd '] shared\Sharer01\subfolder02ro ( RO ) : '[NOPERM] You lack administrator privileges on this mailbox' Logging on Thunderbird and other IMAP clients ( sylpheed\claws ) as user01 : - It list correctly the shared folders as subscribed folders ; - can't view the mail contents of the sharer INBOX, as desired ; - show the total elements of the sharer INBOX, even if the user01 didnt have access ; If the config is correct, this is somehow what we're trying to accomplish, i have some concerns regarding how it is possible to show the total messages of the remote INBOX without having any privileges . Maybe is something related to the index of that INBOX folder that is somewhat read by the accessing user even if IMAP-wise didnt have any ACL \ rights . I still dont understand why enabling the acl_ignore_namespace setting, results in a : - remote INBOX full control, even if it was not defined in any acl ; - subfolders ACL applied correctly Hope that someone can shed a light on it . Thanks Stefano