This could also be yellow to show away, red to show busy and, other presences such as do-not-disturb, out of office, or, unknown. In the example above, I have a green checkmark which identifies my presence as available. That presence date will look like the screenshot below. When viewing or composing an email in Outlook you can also see the presence of anyone internal in your organization and any external users you have federated presence data with. Skype and Teams share their presence data with Outlook.
If you have recently made the switch from Skype to Teams Only mode in Office 365, you may have lost your presence data in Outlook.
