Mail Service in Apple OS X Server before 4.0 does not enforce SACL changes until after a service restart, which allows remote authenticated users to bypass intended access restrictions in opportunistic circumstances by leveraging a change made by an administrator.
Apple Security Advisory 2014-10-16-3 - OS X Server 4.0 is now available and addresses vulnerabilities in BIND, Wiki server, Xcode server, PostgreSQL, and various other software.