Microsoft 365 - Microsoft Exchange Web Services (EWS) Retirement

Microsoft has announced the retirement of Exchange Web Services (EWS) in Exchange Online, with service disablement beginning on September 29th, 2026. EWS-based integrations, applications, scripts, or services will need to transition to supported alternatives, primarily OAuth apps and Graph API apps, before Microsoft's retirement deadlines.

Exchange Web Services (EWS) is a legacy API that has been used for many years to access Exchange Online mailbox, calendar, tasks, and contact data.

Many third-party applications have historically used EWS to interact with Exchange mailboxes.

Applications that continue to depend on EWS after Microsoft's retirement milestones may experience:

  • Failed mailbox access
  • Calendar synchronization issues
  • Broken integrations with third-party products
  • Service disruptions for automated workflows
  • Failures in custom-developed applications or scripts

The Cloud Services and Applications group in University IT Services has reported on university-wide EWS usage since April 2026. The majority of EWS applications in our environment have already had their OAuth/Graph API equivalents become available. We will continue to provide guidance, migration resources, and timelines as Microsoft releases additional information to assist organizations with the transition.

If you manage an application or service that accesses Exchange Online and are unsure whether it uses EWS, please contact the UWM Help Desk.

Thank you for your partnership and assistance as we prepare for this important Microsoft 365 platform change.


Keywords:
M365, EWS, exchange web services, exchange, exchange online, outlook, mailbox, calendar, tasks, contacts, exchange web services retirement, ews retirement, retirement 
Doc ID:
164350
Owned by:
Adam Z. in UW-Milwaukee Help Desk
Created:
2026-09-21
Updated:
2026-09-21
Sites:
UW-Milwaukee Help Desk