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3 min to readDigital Workplace

Retirement of Exchange Web Services (EWS) in Exchange Online: What You Need to Know

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Daniel ChristConsultant Digital Workplace, Microsoft 365
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Microsoft has published the official timeline for retiring Exchange Web Services (EWS) in Exchange Online. For many years, EWS served as a core protocol for integrating third-party applications, migration tools, and hybrid coexistence scenarios. The future, however, lies with the Microsoft Graph API, which provides modern security capabilities and more advanced functionality. The deprecation of EWS is part of Microsoft’s broader initiative to strengthen cloud security and unify its API landscape.

Key Milestones and Dates

  • July 2018: Microsoft announces that EWS will no longer receive new features.
  • September 2023: Official announcement of full EWS retirement in Exchange Online.
  • January 2024: The “Midnight Blizzard” security incident accelerates the phase-out of EWS.
  • August – October 2025: Temporary EWS blocks in hybrid environments as preparation for new security mechanisms.
  • 31 October 2025: Retirement of the Shared Service Principal used for hybrid functionality (Free/Busy, MailTips, photo sync).
  • 1 October 2026: Global retirement of EWS in Exchange Online – all EWS requests will be blocked.

After this date, access to Exchange Online data will only be possible through the Microsoft Graph API (sources: learn.microsoft.com, neowin.net, thecyberexpress.com, mc.merill.net).

What Does This Mean for Exchange Hybrid?

The impact is especially relevant for organizations operating hybrid environments (Exchange On-Premises + Exchange Online). Many rich coexistence features - such as Free/Busy lookups, MailTips, and profile photo synchronization – still rely on EWS through a Shared Service Principal. This principal was retired in October 2025.

Microsoft now requires organizations to adopt a dedicated hybrid application in Entra ID and transition to Graph-based authentication. Failure to implement these changes will result in functional disruptions, particularly in hybrid calendar integration (thecyberexpress.com, community....ection.com).

Why Is Microsoft Taking This Step?

  • Security: EWS is based on SOAP and exposed to modern attack vectors.
  • Modernization: Microsoft Graph provides REST APIs, granular permissions, and deeper integration with Microsoft 365 services.
  • Consolidation: A unified API surface across Microsoft 365 (Exchange, Teams, SharePoint, OneDrive).

Recommended Actions for Organizations

  1. Inventory all applications that rely on EWS (migration tools, third-party apps, internal scripts).
  2. Plan the migration to Microsoft Graph – assess feature parity and identify required adjustments.
  3. For hybrid environments: Implement the dedicated hybrid application and update your configuration no later than October 2025.
  4. Adopt Modern Authentication (OAuth 2.0) and disable legacy authentication methods.
     

Conclusion

The retirement of EWS marks a significant shift toward improved cloud security and platform modernization. Organizations should use the remaining time to adapt their systems and processes. Those who transition early to Microsoft Graph not only avoid service disruptions but also benefit from enhanced security, expanded capabilities, and a future-ready API foundation.

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Do you have questions about the retirement of Exchange Web Services?

Whether you need clarification or hands-on support, feel free to contact us. We’re here to guide you through the transition.

Do you have questions about the retirement of Exchange Web Services?

Whether you need clarification or hands-on support, feel free to contact us. We’re here to guide you through the transition.

Author

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Daniel Christ
Consultant Digital Workplace, Microsoft 365