Presence is part of a user's profile in Microsoft Teams (and throughout Office 365) that indicates the user's current availability and status to other users. By default, anyone in your organization using Teams can see (in nearly real time) if other users are available online.
Teams presence in Outlook is supported on the Outlook 2013 desktop app and later.
Source: https://docs.microsoft.com/en-us/microsoftteams/presence-admins
Request:
GET /api/mt/emea/beta/users/first.last@example.com/externalsearch HTTP/1.1
Host: teams.microsoft.com