[Dovecot] dovecot-keywords problem with MDN

[Mauro D.]

Hi all,
I have Dovecot 1.2.13 installed.
My clients ask why Disposition-Notification is requested every time the 
mail is moved on a new IMAP folder...

I take a look into dovecot-keywords file and I see that:

1) I have only one row
    0 NonJunk

2) dovecot-keywords file is not present inside every directory.

How I can restore normal status? Where is probably the problem?

Thanks
Mauro D.