Four years ago, the 90,000 workers at Atos, a global IT-services company based in France, averaged 15 to 20 hours a week reading and writing e-mails to one another. E-mail “was becoming a burden to our employees rather than an enabler,” says human resources chief Philippe Mareine. So management issued a startling request: Stop it. Instead of e-mailing, employees were urged to communicate through an in-house social network called BlueKiwi.

Atos isn’t the only business trying to increase productivity through social networking, but it’s the only big corporation that’s tried to more or less banish e-mail among co-workers. The $12 billion-a-year company says its internal e-mail volume has fallen 70 percent since 2011, to an average of six messages per person each day. Switching to social networking “has changed how we manage and collaborate,” says Mareine. Although there’s no evidence that Atos’s “Zero E-mail” campaign contributed to the 60 percent jump in the company’s operating margins over the past four years, executives say it’s dramatically improved efficiency. Atos is now pitching BlueKiwi to IT-services clients.

Like other corporate social networks, such as Slack, HipChat, and Yammer, BlueKiwi lets employees create online groups where they can exchange information or work together on projects. Co-workers can review one another’s documents and videos through the network and post comments on them there rather than generating a blizzard of reply-all messages. A separate instant-messaging app and a digital meeting tool complete the package.

One group of Atos consultants used the network to set up an internal help desk where they assist each other in answering client queries. The time needed to resolve queries dropped to 45 minutes from the two hours it took when the consultants helped each other via e-mail, the company says. Atos client Albéa Group, a French manufacturer of cosmetics packaging, has used BlueKiwi to facilitate communication between researchers and factory managers as they develop prototypes for products. The network “changed our method of working,” says Eric Lafarge, Albéa’s vice president for information systems. “It’s become more horizontal, less hierarchical.”

The Radicati Group, a consultant that tracks e-mail use, estimates the average businessperson sends and receives 112 messages daily. In most cases, e-mail “is a horrible tool for collaboration,” says Charlene Li, an analyst at consulting firm Altimeter Group. The constant ping of the inbox is distracting, and long e-mail threads with multiple recipients can become hopelessly tangled, leaving confusion about who took part in a discussion and what was decided, Li says. Yet a study by Altimeter this year found that typically when companies set up internal social networks, many workers don’t use them. That starts at the top, according to Li: If executives don’t use the new tools, the rank and file don’t either.

At Atos, Chief Executive Officer Thierry Breton says he hasn’t sent an internal e-mail in years. Breton gave managers a nudge by changing the bonus system to reward those who used BlueKiwi and had the highest numbers of co-worker “followers.” Management has created “a sense of urgency,” says Andrew Shipilov, a professor of strategy at French business school Insead.

Of course, Atos employees still exchange e-mail with clients, vendors, and other outsiders. (The company says it doesn’t measure the volume of external e-mail.) And there’s a risk that BlueKiwi posts could become as distracting as the inbox, says Robert Pozen, a professor at MIT’s Sloan School of Management who specializes in workplace productivity. Atos employees have created some 10,000 groups on the social network, with topics ranging from sports games to ugly Christmas sweaters. BlueKiwi and its ilk “are good tools,” Pozen says, “but they can be abused just like anything else.”