Doncamilo, thank you for your reply
now inside /var/lib/dovecot/db/shared-mailboxes.db I have this record:
shared/shared-boxes/user/info@futura.local/paolo@futura.local
1
shared/shared-boxes/user/info@futuraservice.it/paolo@futura.local
1
shared/shared-boxes/user/fgiovanni@futura.local/paolo@futura.local
1
With sogo interface i sharing the folder
But in another user i can not view the shared folder