Slack Accuses Microsoft of Illegally Crushing Competition

“For Microsoft, Teams is increasingly where online work is done,” said Wayne Kurtzman, an analyst at IDC, a technology research firm. “It is becoming a platform for Microsoft.”

Slack is making its complaint as adoption of collaboration technology is surging. Slack, Microsoft Teams and Zoom are all experiencing huge demand because of the coronavirus-induced shutdowns that have forced much of the work force to toil from home.

In April, when the company reported its quarterly financial results, Microsoft said Teams had 75 million daily users, more than double the number in early March. At the time, Satya Nadella, Microsoft’s chief executive, said, “We’ve seen two years’ worth of digital transformation in two months.”

Microsoft on Wednesday reported $38 billion in revenue in the three months that ended in June, a 13 percent jump. Its operating profit increased 8 percent to $13.4 billion, or $1.46 a share. Both the company’s sales and earnings per share surpassed Wall Street estimates.

Slack, which was founded in 2014, has enjoyed rapid growth this year. Last month, reporting the results for its quarter ended in April, Slack said its revenue had jumped 50 percent to $202 million. It has more than 122,000 paying customers, typically companies with annual licenses, which was a 28 percent increase from the year-earlier quarter.

Mr. Schellhase, the Slack general counsel, said, “Microsoft is reverting to past behavior.”

But the illegal-tying claim, which Slack makes in its complaint, was not resolved in the federal browser case. Microsoft was found to have engaged in a range of illegal tactics to thwart competition, with contract restrictions and threats. An appeals court upheld those claims but sent the tying claim back to the lower court for reconsideration. The case, which was brought by the Clinton administration, was settled early in the Bush administration.

Slack contends that bundling Teams with Office is “clearly a violation of European law,” said Mr. Prince, the company’s vice president for policy.

Google announced last week that it was more tightly integrating video, chat and email into its GSuite bundle of products. But the difference, Slack says, is that Google is not a dominant company in business software, as Microsoft is.