Salesforce and its workspace messaging app Slack are suing Microsoft at London's High Court over alleged anticompetitive practices relating to its Teams app.
Slack Technologies LLC and related companies filed the lawsuit on April 23, which a Slack spokesperson said was "because Microsoft's practices harmed competition, using tying and bundling of Teams to limit customer choice".
A Microsoft spokesperson said the case lacks merit.
"Slack's lackluster growth, compared to Zoom and Teams, was based on inferior capabilities when COVID-19 hit in 2020, and had nothing to do with Microsoft," the spokesperson added.
Slack had in 2020 complained to the European Commission, accusing Microsoft of bundling Teams with its Office product to gain an unfair advantage over rivals. The U.S. software giant avoided a potentially hefty fine by promising reduced prices for Office products excluding Teams in an agreement with the European Commission last year. The filing of the lawsuit came in the same week that London's Competition Appeal Tribunal certified a mass lawsuit alleging Microsoft overcharged British businesses to use Windows Server software on cloud computing services provided by rivals.
Microsoft disputes the allegations made in that case.
Published on April 28, 2026