Microsoft Exchange Web Services (EWS) and other messaging application programming interfaces (API) aren't supported when you access the Microsoft Teams data that's stored in a user's mailbox. Third-party applications aren't allowed to access or use Teams data in mailboxes. Teams can change its location and use of data at any time. Therefore, using email APIs such as EWS, Exchange REST, MAPI, or Outlook Object Model makes the process vulnerable to code failure.
Access to Teams data is supported only by Microsoft Graph. Fully supported access to Teams message data is available through the Microsoft Teams Export APIs. Teams Export APIs enable you to export one-on-one (1:1) chats, group chats, meeting chats, and channel messages from Microsoft Teams.
If your organization's applications have to export Microsoft Teams messages, you can extract them by using the Teams Export APIs. For more information about the API references for Microsoft Teams, see Use the Microsoft Graph API to work with Microsoft Teams. You can also subscribe to change notifications by creating a subscription for Teams resources.