Salesforce now loves Microsoft so much, it invited Satya Nadella to speak at its huge fall conference

Microsoft had a lot more enemies before Satya Nadella became CEO a year and a half ago.

One of the most vocal leaders to express his frustration was Salesforce CEO Marc Benioff, who once said of Nadella's predecessor Steve Ballmer, "[He] did everything he could to not have a relationship with Salesforce."

Now, the two companies appear to be closer than ever.

In May 2014, they announced their first major partnership that connected Salesforce's CRM software to Microsoft's various cloud offerings, and followed it up with another partnership deal in October.

Benioff frequently lauds Nadella in public. "Before, we just were not able to partner with Microsoft. Satya has opened a door that was closed. And locked. And barricaded," Benioff told Wired about Nadella.

In another telling sign of Microsoft's shifting attitude, Nadella has now committed to appear at Dreamforce, Salesforce's big annual conference in September, as one of its keynote speakers.

Although Salesforce didn't make any formal announcement, Nadella's photo was included in Dreamforce's keynote speaker list released about two weeks ago. Salesforce confirmed to us that Nadella will be the first Microsoft CEO to speak at Dreamforce.

Dreamforce is Salesforce's biggest event of the year, which brings hundreds of thousands of guests from all around the world. It's always had a star-studded lineup of speakers in previous events, including Sheryl Sandberg, Marissa Mayer, and Hillary Clinton.

But Dreamforce has never had a notable guest from Microsoft. Its VP of education marketing, Tony Prophet, went on stage with Benioff at last year's event. Even then, Benioff remarked, "A year ago at Dreamforce, we would not have thought Microsoft would have been here, on stage. It's a shock."

Microsoft reportedly offered to buy Salesforce earlier this year, but the deal fell through after Benioff countered with a much bigger price.