If you're a Teams user, you'll periodically receive missed activity emails in Outlook to let you know what you've missed when you've been away from Teams.
The missed activity emails show the latest replies from the conversation, and allow you to respond directly from within Outlook.
Replying to missed activity emails is not supported in some older versions of Outlook for Windows. Go here for more information.
Replying to missed activity emails is currently not supported in Outlook for Mac.