User for Shared namespace?

[Oliver Block]

Hello everyone,

when issue  a namespace command to cyrus imapd,

00000006 NAMESPACE

you one receives the following response:

* NAMESPACE (("INBOX." ".")) (("user." ".")) (("" "."))
00000006 OK Completed

So I assume that creating a mailbox in shared namespace (("" ".")) goes
like this (cyradm)

createmailbox comp.mail.imap

At least a LIST returns

* LIST (\HasNoChildren) "." "comp.mail.imap"
 . comp.mail.imap

But how to create a user who is entitled to post to this mailbox? And
which privs are required?

TIA,

Oliver Block