Pst Mail Sync runs on a PC with Windows. It silently waits for connections from your iOS device and serves pst files. You device will automatically detect PCs running Pst Mail Sync on its WiFi network.
For more information, read section "Managing PST Files" in the
Pst Mail Manual
Pst Mail Sync runs on Windows XP or higher. It needs a 32-bit Java runtime environment and Bonjour.
You may obtain Java, from http://www.java.com/download
Bonjour usually is installed automatically with iTunes: http://www.apple.com/itunes/download
If you do not want to install iTunes, you may install Bonjour only: http://support.apple.com/kb/DL999
Bonjour is the underlying software that provides automatic discovery of network services. Among other things, it allows your iPhone/iPad to automatically find computers running Pst Mail Sync.
Bonjour is developed and distributed by Apple.