[Dovecot] difference between namespace auto=subscribe and autocreate plugin

[Igor Zinovik]

  Hello.

I read docs, but still do not understand difference between following
configuration options:

namespace inbox {
        # Create and subscribe to folder
        mailbox Drafts { auto=subscribe }

and `autocreate' plugin

plugin {
        autocreate = inbox.Drafts
        autosubscribe = inbox.Drafts

On wiki page that describes `autocreate' plugin i read:
... mailboxes that must always exist for all users.

So even if user delete Drafts IMAP folder on next connection server will
create it.

Is `mailbox' undocumented feature?  I see it only in configuration file,
but wiki does not mention it.