Until April 1, 2020, unlimited Priority Notifications in Microsoft Teams were available for all users. Since April 1, 2020, licensed users are able to send Priority Notifications according to the terms of their subscription. Microsoft Teams Premium Messaging is available as an add-on to Microsoft 365 and Office 365 offers that include paid Microsoft Teams.
With Microsoft Teams Premium Messaging, messages tagged as urgent will notify recipients every 2 minutes, for a period of 20 minutes. It also enables targeted communications in chats, channels and tasks.
For further information on Microsoft Teams Premium Messaging, please visit: https://docs.microsoft.com/en-us/microsoftteams/teams-add-on-licensing/pri-message.