Exchange Web Services (EWS) End of Support: What You Need to Know
Effective October 1, Microsoft will make changes to Exchange Web Services (EWS). EWS is a legacy technology used primarily by non-Microsoft email applications to connect to Exchange for email and calendar access.
To help minimize disruption, EWS connections will be allowed for an additional six months beyond October 1. This temporary extension is intended to give email application developers additional time to release updates that support Microsoft's modern authentication and connectivity methods. Starting April 2027, Microsoft will no longer allow any connections to EWS.
Who may be affected?
If you use a non-Microsoft email application such as Evolution, Apple Mail, Thunderbird, or similar clients, your access to email and calendar services may be affected.
Who is not affected?
- Microsoft Outlook users: No action is required at this time.
- iPhone and iPad users: Native iOS and iPadOS mail applications are not affected by this specific EWS end-of-life change. These applications use Exchange ActiveSync (EAS) or Microsoft Graph APIs rather than EWS.
Need Help?
If you experience issues accessing your email through a mail client after October 1, please contact the IMSS Help Desk (https://servicenow.caltech.edu, 626-395-3500, [email protected]).
We appreciate your patience as we work through this transition and will share additional information as it becomes available.