Research In Motion (RIM) plans to expand its BlackBerry mobile e-mail service beyond its current eight million subscribers by opening it up to rival devices.

The move, designed in part to establish BlackBerry as a consumer service, and not just a gadget for corporate customers, comes as mobile services fast emerge as the next battleground for internet groups.

Apple's iPhone, for instance, will offer a free "push" e-mail service from Yahoo!. At the device's launch in January, Jerry Yang, the Yahoo! co-founder said: "It's basically like having a BlackBerry."

In an effort to guard its lead in the mobile e-mail market, Canada-based RIM has developed a piece of “virtual” software that allows smartphones that run on Microsoft’s Windows Mobile 6.0, a specialised operating system, to join the BlackBerry network.

Once installed, the software will provide users with access to BlackBerry applications such as e-mail, telephony, calendar, an address book and instant messaging.

Users who download the virtual application will see the same rows of icons that appear on the screens of BlackBerry devices - an advance on earlier BlackBerry collaborations with groups such as Nokia and Palm.

The software, not yet priced, is due to be launched this autumn in the US. BlackBerry plans to sell it through an online store and wireless carriers including AT&T.

The company did not elaborate on plans to roll out the software in the UK, but Orange’s business services division announced earlier this month that it will launch the first smartphone to run Windows Mobile 6.0 on the British market.

Mike Lazaridis, the RIM president, said: “Extending BlackBerry applications to a broader range of devices is an important element of RIM's strategy to provide an open platform that supports industry standards.”

The part played by the BlackBerry in modern commerce was highlighted last week when the network collapsed across North America. The outage cut off about five million users, among them thousands of lawyers and bankers working on deals.

The company said that the outage was caused by a bungled software upgrade, ruling out an attack by hackers or capacity constraints.

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