What happens when an O365 user surpasses 2000 API calls per day?

AaronHamilton 

Outlook REST APIs accessed via https://outlook.office.com/api or https://outlook.office365.com/api), and on the Outlook-related endpoints of the Microsoft Graph (accessed via https://graph.microsoft.com). We wanted to give developers some advanced warning to make sure you were prepared!

What's the limit?

The limit is 10000 requests per 10-minute period, per user (or group), per app ID. This means that your app can make at most 10000 requests to a single user's mailbox in a 10-minute period. If your app is requesting data from multiple users simultaneously, requests to one user do not impact the limit for another user.

What APIs are subject to this limit?

Outlook APIs

All APIs accessed via https://outlook.office.com/api or https://outlook.office365.com/api, including:

• Mail API
• Calendar API
• Contacts API
• Tasks API
• People API
• Photo API