Mobile device makers Palm Inc. and Research in Motion Ltd., once bitter rivals, said yesterday that they are now collaborating on technology that would allow users to access e-mail from RIM's BlackBerry service on Palm's Treo smartphone.

The partnership would allow customers to have the best of two cutting-edge worlds -- a wireless e-mail service that is used by millions of professionals combined with an increasingly popular device that not only handles e-mail but also makes voice calls, plays games and music, surfs the Web, and acts as a personal data assistant.

The BlackBerry service will be available early next year on new and existing Treos that run on the Palm software. In the United States, RIM's e-mail functionality is currently available only on its BlackBerry-branded devices.

"This is an opportunity for us to expand the pie for a market still in its infancy," said Page Murray, Palm's vice president of marketing. "We need to be flexible and we need to chase the business wherever it goes."

But analysts offered differing views on which company will end up ahead in the arrangement.

"It's a win for RIM," said NPD Group Inc. analyst Neil Strother. "It puts the RIM software on another device. It's just more confirmation that they have a winning e-mail solution."

Pablo Perez-Fernandez, an analyst at research firm ThinkEquity Partners LLC, said Palm can potentially gain the most.

Customers are demanding more flexibility from the gadgets they use -- both from a personal and business perspective, he said. The Treo, with the ability to download and install a variety of applications written for Palm devices, offers more flexibility and is likely to be the device of choice for tech-savvy mobile professionals.

He estimates that roughly two-thirds of RIM's 3.65 million e-mail subscribers use the BlackBerry device only because it is the product that their employers have selected for them. Those customers might otherwise have chosen the Treo, he said.

Both Palm and RIM, pioneers in their respective markets, have had to radically reinvent themselves in recent months as consumers and companies decide how they want to stay organized and connected to the Internet and e-mail networks.

Last month, Palm announced an upcoming version of its Treo smartphone that will run on Microsoft's Windows Mobile software.

That product will be available early next year.

RIM, meanwhile, is fighting off a fresh wave of competing products, patent-infringement claims related to the BlackBerry and cooling sales. Last quarter, BlackBerry subscriber growth declined 8 percent compared with the previous quarter, despite the growing popularity of mobile e-mail devices as a product category.