The E.U. said Microsoft’s strategy of offering those products as part of a unified software package “may constitute anti-competitive tying or bundling.” The investigation stems from a complaint submitted by the workplace communications platform Slack, which also offers videoconferencing services.

“Remote communication and collaboration tools like Teams have become indispensable for many businesses in Europe,” said Margrethe Vestager, the executive vice president for competition policy for the E.U.

“We respect the European Commission’s work on this case and take our own responsibilities very seriously,” a Microsoft spokesperson told The Washington Post in a statement. “We will continue to cooperate with the Commission and remain committed to finding solutions that will address its concerns.”

Concerns about Microsoft’s outsize power gathered steam in 2020 when Slack filed an initial complaint with E.U. regulators, raising concerns about the unity of Teams and Office. Slack’s workplace communications platform became integral to many businesses’ operations thanks to pandemic-induced social distancing policies — a shift that threatened email communication services such as Microsoft’s Outlook. Zoom became a dominant videoconferencing service, while Microsoft’s Teams and Slack’s Huddle feature offer a similar function.

Slack alleged that Microsoft had illegally forced users to install certain products and had blocked their removal. The company asked the European Commission to order Microsoft to separate Teams from Office and charge a market rate for Teams.