From Zarafa wiki
In order to update Z-Push you can download the new .tar.gz from http://z-push.sf.net.
Required: login as root or use sudo.
In this example x-x is replaced for the version number, for example 1-5.
We will assume that you installed Z-Push in /var/www/z-push.
Important: The state folder should be kept when updating Z-Push.
Also please make sure to read the release notes, as there could be special things which require attention!
If you have made changes to the config.php, please make a backup before following the steps below.
Steps are as follows:
wget http://download.berlios.de/z-push/z-push-x.x.tar.gz tar -zxf z-push-x-x.tar.gz cd z-push-x-x cp -R * /var/www/z-push/
After completing these steps, your Z-Push will be up-to-date.
To check the current version you can execute (where /var/www/z-push/ is where you installed Z-Push):
grep zpush_version /var/www/z-push/version.php
$zpush_version = "1.5 (502)";