AstraSync™ is a software plug-in for BlackBerry® Smartphones that performs two-way over-the-air synchronization of email, calendar and contact data with a Microsoft Exchange, MailSite Fusion, CommuniGate Pro, Kerio, or FirstClass server.
Once installed, AstraSync communicates directly with an ActiveSync server, and so requires a data connection. This can be any data service configured on the device such as Wi-Fi, BlackBerry Enterprise Server (BES), BlackBerry Internet Service (BIS), WAP, etc. Essentially, if you can get to a web page using a browser on the device, AstraSync should work.
AstraSync can be installed either over-the-air, or using the BlackBerry Desktop Manager and a wire.