I’ve had the opportunity to test the same configuration with a fresh build of the git master branch (2.4.devel) and the issue also occurs there. I see that "mailbox_list_index = yes" is now enabled by default. It can still be disabled via "mailbox_list_index = no" which allows the quota to be calculated correctly.

========== root@ubuntu1804:~# dovecot -n # 2.4.devel (44282aeeb): /usr/local/etc/dovecot/dovecot.conf # OS: Linux 4.15.0-30-generic x86_64 Ubuntu 18.04.1 LTS # Hostname: ubuntu1804 mail_location = maildir:~/Maildir mail_plugins = quota namespace inbox { inbox = yes location = prefix = INBOX. separator = . } passdb { driver = pam } plugin { quota = maildir:Mailbox } userdb { driver = passwd }

(To summarize from my previous message -- other than "mailbox_list_index = yes", second most important part of replication is that there is at least one email in the real inbox and at least one sub-folder named "INBOX" in maildir format)

root@ubuntu1804:~# ls -ld /home/myuser/Maildir/cur/1532529376.M543965P58007.centos7.local\,S\=12712627\,W\=12877782\:2\,S /home/myuser/Maildir/.INBOX.Test/ -rw-rw-r-- 1 myuser myuser 12712627 Aug 14 18:28 '/home/myuser/Maildir/cur/1532529376.M543965P58007.centos7.local,S=12712627,W=12877782:2,S' drwxrwxr-x 5 myuser myuser 87 Aug 14 18:56 /home/myuser/Maildir/.INBOX.Test/

(In the following example usage is doubled, there is only one email)

root@ubuntu1804:~# doveadm quota recalc -u myuser; doveadm quota get -u myuser Quota name Type Value Limit % Mailbox STORAGE 24830 - 0 Mailbox MESSAGE 2 - 0

(In the following example it works correctly with mailbox_list_index disabled)

root@ubuntu1804:~# doveadm -o 'mailbox_list_index=no' quota recalc -u myuser; doveadm quota get -u myuser Quota name Type Value Limit % Mailbox STORAGE 12415 - 0 Mailbox MESSAGE 1 - 0

Best Regards