Microsoft will start blocking older mail connections in Outlook from October 2026
Reviewed by Helen Jones
Microsoft will begin turning off Exchange Web Services (EWS) in Exchange Online on 1 October 2026. Full permanent retirement is planned for around 1 April 2027. EWS is the older connection method many third-party apps and some mail tools still use to reach mailboxes. Microsoft wants those apps moved to Microsoft Graph and other modern paths. Tenants may be able to allow-list some use for a time, but the long-term path is off. The change applies to Microsoft 365 cloud mail, not on-premises Exchange Server. Supported Outlook apps on Windows, Mac, web, and mobile are the path Microsoft points users toward. The main break risk is for custom apps, backup tools, and older clients that still depend on EWS.
Until now, a lot of mail side tools kept working quietly in the background even if nobody in the team could name the protocol. Shared mailbox helpers, older desktop clients, backup or archiving add-ins, and niche calendar sync tools often still spoke EWS while people lived in Outlook and Teams as normal. From October 2026 that quiet layer can start failing. The pain will not look like a Microsoft Graph project. It will look like a familiar helper that suddenly cannot open a mailbox, sync a calendar, or pull mail into a report, while day-to-day Outlook itself still works.
Analysis
Treat this as a trap to avoid, not a feature to study. Make a short list of every non-Microsoft tool that touches your mailbox, shared mailboxes, or calendar, then ask IT or the vendor one question: does this still require EWS after October 2026, and what is the supported replacement.
Source note
Pulse published by Collab365 Spaces, reviewed by Helen Jones on . Cite as "Microsoft will start blocking older mail connections in Outlook from October 2026", Collab365 Spaces. 3 sources referenced.