Dovecot 2.2.16 doesn't rotate mdbox files

Hello,

there's setting in my config file:

mail_location = mdbox:/var/vmail/%Ld/%Ln:INDEX=/var/indexes/%Ld/%Ln

mdbox_rotate_size = 1M mdbox_preallocate_space = yes mdbox_rotate_interval = 1d

As I understand, this settings means that file which contains letters with refcount=0 will be rotated after 23:59 today. I remember letter ID and execute grep whith this one in storage directory. Letter was presented. After that, I removed letter over IMAP protocol, checked and find it again.

On the next day check with grep was repeated and letter was finded. After

doveadm purge -u user@domain

letter was expunged.

What's wrong in my configuration?