Multiuser attachment storage (mail_attachment_dir)

[megaone at yandex.ru]

Was trying to set up attachment storage, but folders are receiving permission only for current user, so if another user is receiving a mail with same attachment he is getting permission denied error on reading hash file. Is it possible to setup global attachment storage to work with all users, at least in domain? mail_access_groups won't help, as folders are given 0 group permission. Umask and setfacl won't help either.