The Mail API Reference has all of the details.

Once the app has an access token, it's ready to call the Mail API. Use one of the supported OAuth 2.0 flows to obtain an access token. In order to call the Mail API, the app requires an access token from the Microsoft identity platform. With the information in this guide, you can implement this in any language or platform capable of sending HTTP requests. You should use the Outlook APIs directly (via ) only if you require a feature that is not available on the Graph endpoints. Microsoft recommends using Microsoft Graph to access Outlook mail, calendar, and contacts. This tutorial will use Microsoft Graph to call the Mail API. It will cover the sequence of requests and responses that an app uses to authenticate and retrieve messages. Unlike the platform-specific getting started guides, this guide focuses on the OAuth and REST requests and responses. The purpose of this guide is to walk through the process of calling the Outlook Mail API to retrieve messages in Office 365 and. We'll go through the same set of steps using raw HTTP requests. If your preferred platform isn't listed yet, continue reading on this page. We'll guide you through the steps to write a simple application to retrieve messages from your inbox. Once you're done exploring the API, come back here and select your favorite platform on the left. You can use your own account, or one of our test accounts. Try out sample REST calls in the Graph Explorer.

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