autoexpunge=30d does not works :(

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