With more than 500,000 organizations on Microsoft Teams and 10 million daily users on Slack, the two companies are best known as competitors in the race to make their messaging apps the portal to everything you need to get your job done.
But today they’re working together to launch a Slack integration in Outlook and an Outlook Slack app to stay on top of your calendar.
The calendar integration and Slack sharing in Microsoft’s Outlook email client are designed to enable people to check their schedule and discuss emails with their team without leaving Slack.
The Outlook Calendar Slack app integrates the Outlook calendar to do things like deliver upcoming event reminder notifications, respond to event invite requests, join video calls, get daily event rundowns, and let you know when you’ve double-booked a calendar event.
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The Outlook Calendar Slack app will also be able to deliver automatic updates to Slack so your Slack status will automatically reflect your calendar, and let you click a button to join WebEx, Skype for Business, or Zoom video calls.
In turn, Office 365 users in Outlook will be able to quickly send an email to a Slack channel. Emails can also be sent to channels with Microsoft Teams.

Above: Outlook app with Send to Slack button
In late 2018, Microsoft OneDrive users first got the ability to preview PowerPoint, Microsoft Word, and Excel files without the need to leave Slack. Today Slack also announced an update to the OneDrive integration to make it easier to search and share those files.
The news today is Slack’s latest example of co-opetition (cooperation and competition) from Slack, whose Actions feature brought the ability to take fast actions with many competing SaaS software services to do things like create a Trello card or start a HubSpot or Asana ticket.
Additional major upgrades to how Slack works are expected ahead of the Frontiers conference, which takes place April 24-25 in San Francisco.