He warned that employee well-being could suffer from an ever-expanding workday that often now creeps well into the night.

Nadella, whose company has studied how remote work impacts collaboration in an effort to improve its Teams software, cited earlier Microsoft research showing that about a third of white-collar workers have a "third peak" of productivity late in the evening, based on keyboard activity.

Productivity spikes before and after lunch, but this third peak illustrates how remote work has broken down already-blurred boundaries between our job and our home lives.

Nadella said managers need to set clear norms and expectations for workers so that they're not pressured to answer emails late at night.

"We think about productivity through collaboration and output metrics, but well-being is one of the most important pieces of productivity," he said. "We know what stress does to workers. We need to learn the soft skills, good old-fashioned management practices, so people have their wellbeing taken care of. I can set that expectation, that our people can get an email from the CEO on the weekend and not feel that they have to respond."

Two out of three employees who consider leaving their job say their employer has not followed through on early pandemic promises to focus on employee mental health, according to a Harris Poll commissioned by online therapy provider Talkspace.