‘You can see the horrible things that Microsoft did to Slack before we bought it’: Marc Benioff warns Microsoft could repeat 'pretty nasty’ Slack playbook with OpenAI amid frayed relationship

Salesforce CEO Marc Benioff claims Microsoft did "horrible things" to Slack prior to its acquisition — and could be ready to repeat its "playbook" of anti-competitive behaviour with OpenAI.

The Salesforce CEO isn't one to mince his words, having previously compared Microsoft Copilot to "Clippy," and called its AI tools a "huge disaster".

In his latest war of words with the tech giant, sparked in a recent podcast appearance, Benioff told SaaStr CEO Jason Lemkin Microsoft did “horrible things” to Slack before it was acquired by Salesforce.

Salesforce purchased the enterprise messaging app in 2020 in a deal worth over $27 billion, The move came four years after Microsoft reportedly decided against buying the platform for $8 billion, choosing instead to focus on Skype and launch Teams.

Slack and Microsoft had a long-running feud, with the former having accused Microsoft of anti-competitive behavior for bundling Teams with Office 365. The company alleged this constituted "illegal behaviour".

Six months later, Salesforce bought Slack and last year Microsoft agreed to unbundle Teams from Microsoft 365 and Office 365.

"You can see the horrible things that Microsoft did to Slack before we bought it," Benioff said. "That was pretty bad and they were running their playbook and did a lot of dark stuff. And it's all gotten written up in an EU complaint that Slack made before we bought them."

Without going into further details, Benioff said Microsoft's treatment of Slack was "pretty nasty", pointing to a similar "playbook" that the Redmond giant has allegedly employed before.

Benioff referenced the ‘browser wars’ with Netscape in the late 1990s and Microsoft’s conduct during that period.

"That playbook should get ripped up and thrown away," Benioff said.

ITPro approached Microsoft for comment on Benioff’s claims, but the company had not replied by the time of publishing.

Benioff thinks OpenAI could be in Microsoft’s crosshairs

Lemkin suggested it was no surprise there is "an inherent aggressiveness in enterprise software," adding that it was funny to think of Microsoft bothering to worry about Slack as Azure is "so rejuvenated right now".

But Benioff warned that the pattern he previously described could happen again with OpenAI and Microsoft.

While Microsoft has invested heavily in OpenAI — and CEO Sam Altman once called it the "best bromance in tech" — the partnership showed signs of stress early this year with an announcement that included changes to exclusivity, though Microsoft retained a right of first refusal.

Reports in December last year also suggested Microsoft had been exploring the possibility of using internal and alternative third-party models to power its flagship Microsoft 365 Copilot service.

The tech giant told ITPro in January that OpenAI “continues to be our partner on frontier models”.

More recently, Benioff noted that OpenAI revealed its technology stack without any mention of Microsoft, hinting that this further highlights the two companies pursuing separate paths.

"That was extremely interesting and you can see how Microsoft is really starting to run a separate playbook against OpenAI," he said.

"I think that's now how Microsoft thinks," he added. "Microsoft is a company that wants to own it all, control it all, if they see a hot company or hot startup, they ask themselves: ‘hey why is that not in our world’.

“They feign an acquisition and then based on that they execute a playbook — or in the case of OpenAI, a partnership is gonna become a competition."

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