The shadow-utils package contains the tool useradd, which is used to create or update new user information. When useradd creates an account, it would create it with improper permissions; instead of having it owned by the group mail, it would be owned by the user's primary group. If this is a shared group (ie. "users"), then all members of the shared group would be able to obtain access to the mail spools of other members of the same group. A patch to useradd has been applied to correct this problem.