Microsoft and Slack have locked horns after the latter filed a competition complaint against the IT giant for using its market dominance in Office to crush the competition.
Slack claims that Microsoft has illegally tied its Teams product into its Office productivity suite, forcing millions of users to install it while also blocking its removal.
The instant messaging vendor also says that Microsoft hides the true cost of its product to enterprise customers.
Slack goes on to state that its own product threatens Microsoft's dominance in business email and its dominance in enterprise software as a whole.
The European commission will now review Slack's complaint and then decide whether it will open a formal investigation into Microsoft's practices.
"We're confident that we win on the merits of our product, but we can't ignore illegal behaviour that deprives customers of access to the tools and solutions they want," said Jonathan Prince, VP of communications and policy at Slack.
"Microsoft is reverting to past behaviour. They created a weak, copycat product and tied it to their dominant Office product, force installing it and blocking its removal, a carbon copy of their illegal behaviour during the ‘browser wars.' Slack is asking the European Commission to take swift action to ensure Microsoft cannot continue to illegally leverage its power from one market to another by bundling or tying products," added David Schellhase, general counsel at Slack.
Microsoft responded to the allegations soon after Slack filed the competition complaint.
It hit back claiming that Slack's product has suffered because it lacks a videoconferencing component.
"We created Teams to combine the ability to collaborate with the ability to connect via video, because that's what people want. With COVID-19, the market has embraced Teams in record numbers while Slack suffered from its absence of video-conferencing. We're committed to offering customers not only the best of new innovation, but a wide variety of choice in how they purchase and use the product," Microsoft said in a statement.
"We look forward to providing additional information to the European Commission and answering any questions they may have."
Microsoft and Slack have been locked in a rivalry since Microsoft first launched its own work chat solution in 2016.
Slack reacted by publishing an open letter to Microsoft in a form of an advert in the New York Times. In the advert, Slack threw the gauntlet down to Microsoft and suggested that Teams was copycatting its own solution.
"We realised a few years ago that the value of switching to Slack was so obvious and the advantages so overwhelming that every business would be using Slack, or 'something just like it', within the decade," the letter stated.
"It's validating to see you've come around to the same way of thinking. And even though - being honest here - it's a little scary, we know it will bring a better future forward faster.
"However, all this is harder than it looks. So, as you set out to build 'something just like it', we want to give you some friendly advice."
Meanwhile, last October, Microsoft claimed that it had grown its daily active user count by 50 per cent to 20 million since July, compared to 12 million for Slack.
But Slack's CEO Stewart Butterfield has called into question Microsoft's methods in recording daily active users. He claims that Microsoft's definition of a daily active user is different to Slack's.
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Slack accuses the IT giant of illegally crushing the competition, while Microsoft hits back claiming Slack has suffered through lack of video conferencing