We’re about a month away from the deadline we communicated in our blog post and Message Center posts, and we want to remind our customers before we start blocking traffic.
The preview program for REST API access to on-premises mailboxes in an Exchange hybrid configuration has ended. Beginning June 2023, we will return errors for requests made against on-premises mailboxes.
Over the past few weeks, we have sent Message Center (MC) posts to the affected customers; we encourage you to check your Message Center for posts MC541164 and MC541165. If you have received those messages, you have some apps that might be affected; if you don’t have the messages, this change will not affect your tenant.
As we said in the MC posts, there are several actions you can take to avoid disruption when this traffic is blocked.
- Identify the App ID responsible for the traffic. You can do this by searching for the App ID in the Microsoft Entra admin center.
- Once the App is identified, you have three options:
- Move the mailbox to Exchange Online;
- Modify the application to use EWS (if it needs access to an on-premises mailbox);
- Ignore the traffic and accept that it will be blocked.
We know some of our customers and partners have built solutions based on this preview which we released years ago. We understand that updating your code to remove this dependency might be time consuming. However, we need to invest our resources in building highly scalable, secure, and robust solutions that our strategic imperatives and focus on the technologies we see our customers adopting.
The Exchange Team