The service will be included with the Premier and Education editions of Google Apps. End-users will find their Google messages pushed to the e-mail client on their BlackBerry, and messages sent from their phones will appear to have come from their organization's Google mail account.

They'll be able to access their organization's Google address list from their phone, and to synchronize contacts and calendar items. The service is in beta and will be commercially available in July.

The service requires organizations to add a piece of software to their BlackBerry Enterprise Server (BES), and that software is available today only for the Microsoft Exchange version of BES. The software connects back to Google's mail servers, rather than the company's Exchange server, to synchronize mail, contacts and calendar items.

The service steps up Google's rivalry with Microsoft in the enterprise, but it does have some weaknesses. Initially, calendar items can be synchronized only from the server to the user's phone. So if a user makes a new calendar entry on their BlackBerry, it won't be synched back to their online calendar. An upgrade that supports two-way synch should come by the end of the year, said Raju Gulabani, product management director for Google Apps.

In addition, the service will initially support only 250 users per BES. A BES can typically handle at least 500 users, sometimes many more. If an enterprise wants to support more than 250 Google Apps users it will have to use an additional BES.