Salesforce.com Inc. agreed to buy Slack Technologies Inc. for $27.7 billion in cash and stock, giving the corporate software giant a popular workplace-communications platform in one of the biggest technology deals of the year.

The transaction, Salesforce’s largest-ever acquisition, is expected to close by the end of July, the San Francisco-based company said Tuesday in a statement. Slack investors will receive $26.78 for each company share as well as 0.0776 share of Salesforce—representing a 55% premium to Slack’s price on Nov. 24, the day before reports about deal talks between the companies.

Salesforce Chief Executive Officer Marc Benioff has orchestrated more than 60 acquisitions in 21 years, taking his company from dot-com era upstart to a titan of cloud computing. The Slack deal would give Salesforce, the leader in programs for managing customer relationships, another angle of attack against Microsoft Corp., which has itself become a major force in internet-based computing. Microsoft’s Teams product, which offers a workplace chatroom, automation tools and videoconference hosting, is a top rival to Slack.

“Together, Salesforce and Slack will shape the future of enterprise software and transform the way everyone works in the all-digital, work-from-anywhere world,” Benioff said in the statement.

Stewart Butterfield, Slack’s co-founder and CEO, will continue to run the business as a Salesforce unit when the deal is completed, the companies said.

—Bloomberg News