The APS Package 7.2-x requires POA 5.0 or higher, Plesk 11.5 or higher and Open-Xchange 6.22.3 or higher / OX App Suite 7.2.1 or higher.
OX App Suite is a centralized cloud environment that lets you take control of your digital life from anywhere:
It provides and centralizes email, contacts, calendar and tasks.
It provides cloud based file storage and document management/viewing/editing.
It provides a digital life management portal that lets you access all this and more regardless of device or operating system.