New Microsoft Teams is just AWESOME, quick but useful post below shows how you have this preview feature to make your life EASY!
Open Microsoft Teams admin center [Ask admin in your organization if you don’t have access] and follow path Teams > Teams update policies > Click on an existing policy or Create New > follow step 1 and step 2 below.
Let the change happen!
Get it, Preview new Teams!
Experience teams across tenants and get notifications from multiple tenants accounts. This is PRETTY COOL!