[Dovecot] "doveadm mailbox create" oddities

[Andre]

Hi to all!

I’m trying to understand the usage of "doveadm mailbox create”.
If I do, as root:

# doveadm mailbox create -u __public__ sys/test    
doveadm(__public__): Error: Can't create mailbox sys/test: Permission denied

but if I do:

# doveadm mailbox create -u __public__ test

every thing is OK.

“sys" is a shared maildir folder, that is visible in the client as "#Public/sys”.
__public__ is the user that owns Public folders, here is the complete details:

userdb: __public__
  uid       : 10002
  gid       : 8
  home      : /var/mail/domainname/__public__
  mail      : maildir:~/maildir:INBOX=~/maildir/INBOX:LAYOUT=fs:INDEX=~/indexes/


Do I have to add root with proper permissions to ACL?

TIA
Andre