Slack, the San Francisco-based workplace collaboration platform, has tapped Microsoft’s range of open APIs to integrate services from rival Office 365 into its software.

The company now offers 1,500-plus integrations, from Cisco to Dropbox.

Slack had previously enabled Microsoft Azure Active Directory and OneDrive for its users, but as of this week it has integrated several Office 365 tools to make it easier to collaborate with colleagues, including the ability to sync Outlook’s calendar.

“Slack is breaking down walls for its customers and allowing them to collaborate seamlessly across their entire productivity suite for maximum flexibility” the company said, announcing rich file previews of O365 files (PowerPoint, Excel, Word), Outlook calendar syncing and the promise that users will soon be able to send Emails to Slack from Outlook, via a pending Outlook email add-on.

The Outlook calendar integration will let Slack users receive and respond to Outlook event invites via Slack; join Skype for Business, Webex or Zoom calls with a click and automatically sync users’ calendars and Slack status.

Slack Continues to Remain Popular

Slack, launched four years ago, reported over eight million daily active users (DAU) using the service across more than 500,000 organisations in 2018.

Of this number, some three million are paid users.

The company raised $250 million from investors in a funding round led by Softbank last September that valued the company, on paper, at just over $5 billion.

Slack said at the time of that round that it has “yet to spend much of our existing capital,” and is hoping for “operational flexibility”.

Slack said in a blog post: “We pursued this additional investment to give us even more resources and flexibility to better serve our customers, evolve our business, and take advantage of the massive opportunity in front of us.”

“Our mission is to make people’s working lives simpler, more pleasant, and more productive, and we are grateful for the support along the way.”

See Also: Google Offers Third-Party Hardware Bundles as it Pushes Enterprise Hangouts Use