Salesforce and Slack sue Microsoft in London over Teams bundling practices

Salesforce and Slack have brought Microsoft back to the center of a familiar antitrust fight, filing a lawsuit in London’s High Court over the way Teams is bundled with the company’s wider Office business. A Slack spokesperson said the case concerns Microsoft’s “tying and bundling” of Teams, a practice the companies say squeezes out rivals and leaves business customers with less choice.

The case reaches well beyond one workplace chat app. Teams was launched globally on March 14, 2017, and Microsoft said it was available in 181 markets and 19 languages at launch, giving it an immediate distribution advantage inside Office 365. That reach is exactly why competitors and regulators have treated the product as more than a simple add-on. In the European Union, officials found that since at least 2019 customers could not buy Office 365 and Microsoft 365 suites without Teams, a packaging strategy that raised concerns about whether Microsoft was using its dominance in productivity software to steer buyers toward its own collaboration tool.

Slack first challenged that strategy in 2020, filing a competition complaint with the European Commission on July 22 of that year and accusing Microsoft of tying Teams to Office, force-installing it for millions, blocking removal and hiding the true cost to enterprise customers. The Commission later accepted Microsoft commitments in September 2025 requiring versions of Office and Microsoft 365 without Teams, lower prices, interoperability improvements and data-portability measures. Microsoft’s own licensing update later said that as of November 3, 2025, enterprise and business suites with Teams were again available to all customers, underscoring how regulatory pressure had already changed product design and pricing.

The London lawsuit arrives as Microsoft faces another major legal challenge in Britain. On April 21, 2026, the Competition Appeal Tribunal certified a separate collective action over cloud licensing that was brought on behalf of nearly 60,000 businesses and valued at about £1.7 billion, or $2.8 billion. That case alleges Microsoft overcharged companies using Windows Server on rival clouds such as Amazon Web Services, Google Cloud and Alibaba Cloud.

Taken together, the two British proceedings show how competition disputes around Microsoft now span messaging, productivity software and cloud infrastructure. For businesses that depend on Microsoft’s stack, the stakes are not abstract. The outcome could influence how suites are priced, how tightly products are bundled and how easily customers can move between chat, video and cloud tools, in Britain and far beyond.