Microsoft published a guide on its Tech Community blog for apps that broke when Exchange Web Services (EWS) was switched off in Exchange Online. EWS is an older way for apps to reach mailbox data. Microsoft listed outdated Outlook for Windows and vendor backup tools as affected. Users may see repeated password prompts or an error saying EWS is unavailable. BleepingComputer reported on 22 October that Microsoft said in February it would block EWS by default from 1 October 2026.
Microsoft said only a tenant administrator can turn EWS back on, and its support staff cannot do it for them. Admins can use the Baseline security mode page or Exchange Online PowerShell. Microsoft said the change usually takes under an hour, and rarely up to four. Edits to the allow list take 24 hours. Microsoft said re-enabling will stop working in April 2027. BleepingComputer gave 1 April 2027 as the final shutdown date. The sources do not say how many customers are affected.
Any team on Microsoft 365 that relies on older Outlook, backup tools or in-house apps now has a hard deadline. Microsoft says the lasting fix is a newer app version without EWS, from the vendor or through code changes. BleepingComputer reported that Microsoft points developers to Microsoft Graph, and that on-premises Exchange keeps EWS.