how to expunge DELETE.user.username from mailboxes db ?

[Riccardo Veraldi]

Hello,
after removing a mailbox with cyradm (dm user.username).

I have plenty of DELETED.user.username  in the mailboxes database.

for example given user.username which has been deleted, i still ahave 
the following entries


/usr/lib/cyrus-imapd/ctl_mboxlist  -d  | grep -i username

DELETED.user.username.5667F5BC    0 default username lrswipkxtecda    
cyrus    lrswipkxtecda
DELETED.user.username.Drafts.5667F5C2    0 default username lrswipkxtecda
DELETED.user.username.SPAM.5667F5C3    0 default username lrswipkxtecda
DELETED.user.username.Sent.5667F5C3    0 default username lrswipkxtecda
DELETED.user.username.Trash.5667F5C5    0 default username lrswipkxtecda


how can I get rid of these entries in the mailboxes database ?
after years it is full of DELETED entries.

thank you