autoexpunge=30d does not works :(

[Peter Hodur]

Hello,

just upgraded to Dovecot 2.2.27 and altered dovecot.conf to contain
autoexpunge directive for Spam mailbox (yes it's migrated from Courier 3
years ago):

namespace inbox {
        prefix                                                  = INBOX.
        separator                                               = .
        inbox                                                   = yes

        mailbox Archive {
                auto                                            = subscribe
                special_use                                     = \Archive
        }
        mailbox Drafts {
                auto                                            = subscribe
                special_use                                     = \Drafts
        }
        mailbox Spam {
                auto                                            = subscribe
                special_use                                     = \Junk
                autoexpunge                                     = 30d
        }
        mailbox Sent {
                auto                                            = subscribe
                special_use                                     = \Sent
        }
        mailbox Trash {
                auto                                            = subscribe
                special_use                                     = \Trash
        }
}

As I hope, when user logout (POP3 or IMAP) or after Postfix delivers mail
via LMTP, Dovecot should check Spam folder for emails, which have ctime
older than 30 days and deletes this emails.

Recently I have tried this. I have tried login / logout and nothing
happend. I have tried turning log verbosity to debug but I can not find any
note in debug.log according to this.

I would like to kindly ask someone for which this directive works to help
me, what is wrong with my config or how can I debug it and find error.

Thanks

Pete