Microsoft announced in November 2020 that it would phase out the Outlook REST API beta and Outlook REST API v2.0 over the next two years during a transition period, and after the two-year period was coming to an end, Microsoft said it was putting the phase-out plan on hold based on customer feedback.
However, Microsoft said that although this phase-out plan has been put on hold, customers should not think that these two APIs will be retained for a long time, and will continue to promote the phase-out plan according to the situation. Microsoft said that although the phase-out plan has been postponed indefinitely, it is expected to restart in 2023 when customers will be notified 6 months before the deadline.
The Outlook REST API is mainly used by developers to manage mailbox data, calendars, contacts, push notifications, etc. in the application. However, Microsoft has considered it an obsolete product since 2020 and has been encouraging customers to migrate to Microsoft Graph.