By Alex Kleiderman
BBC News business reporter
Blackberry's creators are trying to spread its appeal
The Canadian company behind the Blackberry, the wireless e-mail device beloved by business executives and celebrities, is bearing the fruits of a year of rapid subscriber growth.
Yet, as the sector expands, market leader Research In Motion (RIM) faces challengers in the shape of Microsoft, other software developers and mobile phone manufacturers.
"Employees are very much dependant on e-mail and secure wireless e-mail has a very large potential adoption," says Monica Basso, analyst at Gartner Research.
"RIM may have created the demand but in a few years there will be more players in the picture.
"The Blackberry model isn't going to be a viable option for everyone."
The Blackberry became an icon in the late 1990s as the device that provided a link between on-the-move executives and their office networks by automatically delivering e-mail through so-called push technology.
Waterloo, Ontario-based RIM has traditionally made money by selling the Blackberry, its software and services to large companies as a package.
Over the last two years, however, it has targeted small and medium firms and promoted its use among a larger spread of the workforce.
Deals with mobile phone carriers in over 30 countries have helped expand its reach.
RIM has also introduced combined Blackberry and mobile phones and licensed software for use in handsets from other manufacturers including Nokia, Siemens and Motorola.
It took RIM five years to attract one million subscribers but the firm has indicated it is currently adding users at a rate of more than 180,000 a month.
The company says it now has more than 2.51 million subscribers, with the 4 million mark in sight by the end of the year.
"RIM is trying to move beyond the hardcore large enterprise market but in terms of focussing on a more consumer offering, that's nowhere in the near future," said Rob Sanderson, analyst at American Technology Research.
A growing line of rival developers are winning contracts from major companies.
Fans of the software offerings from the likes of Good Technology, Visto, Smartner and Intellisynch say they can be installed on a wider choice of devices.
1984: Founded in Ontario, Canada, as a wireless data technology developer
1996: Introduces the world's first two-way messaging pager
1997: Lists on the Toronto Stock Exchange
1999: First Blackberry e-mail device released
1999: Lists on the Nasdaq
2002: Voice support integrated into Blackberry
Microsoft too has licensed its e-mail technology to mobile phone and PDA manufacturers, while working on a new software package that could appeal to the security-conscious users of the Blackberry.
RIM's share price has taken hits over the year on competition fears but no-one is writing the company off.
Rob Sanderson says RIM is constantly adding new features to its product and predicts this can help it retain a lead in the lucrative corporate sector where its technical infrastructure is highly valued.
"RIM had incredible vision and made very smart decisions early and that allowed it to get on a learning curve many years ahead of potential competitors," he adds.
On Tuesday, RIM said sales for the 12 months ending 26 February were $1.35bn (£717m), up from $594m in the previous year.
Profit has been rising although for the fourth quarter it posted a loss of $2.6m on the back of the settlement of a patent infringement lawsuit with NTP.
Some say the $450m settlement has lifted uncertainty from RIM and could prompt more companies and mobile phone manufacturers to take up services.
Meanwhile, takeover bid speculation surrounding RIM has surfaced once again, with mobile phone giant Nokia the latest in a line of suitors reportedly linked to the firm.