Please be aware that the Zarafa apps are soon to be obsolete and will only receive updates for a limited time. In its place you can install the Kopano apps, which are already recommended for new installations. Kopano is currently working on an easy way to migrate all data from the Zarafa apps to Kopano and will provide this in time for the End of Life of this app scheduled for the 30. November 2016.
Z-Push emulates the ActiveSync functionality of a MS Exchange server allowing mobile devices (mobile phones, smartphones, PDAs, tablets) to synchronize with a server via over-the-air ActiveSync (AirSync). Using Z-Push most mobile devices can synchronize without installing any additional software on the device. It allows users to synchronise their email, contacts, calendar items and tasks directly from a compatible server over UMTS, GPRS, WiFi or other GSM data connections in real time.