Slack Technologies announced Wednesday it has filed a competition complaint against Microsoft with the European Commission for anti-competitive practices.

It claims Microsoft abused its market share dominance to snuff-out the competition in breach of European Union competition law by illegally tying its video product, Microsoft Teams, its Office productivity suite, which dominates the market.

The move forces users to install the video conference platform on millions of computers. Slack asserts Microsoft also does not enable users to delete the tool and hides the “true cost” of using the product.

“We’re confident that we win on the merits of our product, but we can’t ignore illegal behavior that deprives customers of access to the tools and solutions they want,” Jonathan Prince, vice president of communications and policy at Slack in a blog post. “Slack threatens Microsoft’s hold on business email, the cornerstone of Office, which means Slack threatens Microsoft’s lock on enterprise software.”

Microsoft Teams is the hub for video collaboration in Microsoft 365, which connects people, content and tools. It’s most useful now, as many employees continue to work from home during the pandemic.

Prince called the complaint more than a Slack vs. Microsoft feud. He wrote that it is a proxy for different philosophies on the future of digital systems, “gateways versus gatekeepers.”

Slack, according to the company, offers collaboration tools designed to replace email as a primary method of communication and sharing. Its workspaces allow companies to organize communications by channels for group discussions and allows for private messages to share information, files, and more all in one place.

David Schellhase, General Counsel at Slack, explains the company just wants fair competition and a level playing field.

The two companies have benefited from the work-at-home surge, due to COVID-19. Still, Slack does offer video conferencing, though it’s not the main reason people use its tools. Its decision to file a formal complaint isn’t unusual or unexpected, especially now as companies fight for market share during the pandemic.