CNN Business  — 

Slack is teaming up with Amazon as it battles Microsoft to be the go-to remote workplace communications tool with the coronavirus keeping more workers at home.

The two companies announced a wide-ranging partnership on Thursday, including Slack’s service rolling out to all Amazon employees. Slack will also use Chime, the communications platform developed by Amazon Web Services, to support its voice and video calling functions.

Slack (WORK) is one of several companies, including Cisco (CSCO), Google (GOOGL) and Zoom (ZM), that have seen a spike in usage of their work collaboration tools as millions were forced to stay home because of the coronavirus pandemic. But the rivalry between Slack (WORK) and Microsoft’s Teams platform has come to the fore in recent weeks, with Slack (WORK) CEO Stewart Butterfield saying in an interview with The Verge that Microsoft “is perhaps unhealthily preoccupied with killing us.”

Slack added a record 12,000 new paying customers in the three months ending April 30, and more than 90,000 new organizations on paid or free subscription plans, it said in an earnings report Thursday. It also reported $201.7 million in revenue for the quarter, a 50% increase from the same period a year earlier.

But neither those numbers, nor the Amazon deal, were enough to cheer investors — the company’s stock plunged around 16% in after-hours trading following the results.

Butterfield also spoke out in support of ongoing nationwide protests for social justice at the beginning of the company’s earnings call, referring to the movement as a “human crisis” brought about by “generations of systemic racism and white supremacy.”

“This is a crisis of our own making, not nature’s, and it will take all of us to repair it, to demand that it is repaired,” he said. “Silence is a luxury we cannot afford.”