Mailboxes appears in another Mailbox without adding them in Outlook

Hi All,

Since I have updated my Exchange servers 2010 farm with SP2 - U4 v2, user's mailbox appears in another user's mailbox when I give full right permissions.

Normally, it desappear when I remove full right permissions on the mailbox.

Unfortunately, some Mailboxes do not go away even if full right permissions are removed.

I would like to know how I can clean the mailbox in which many old mailboxes appear without being accessible?

Any Q?

Thanks!