Microsoft Exchange Web Services Ending Oct. 1, 2026

Summary

Microsoft will begin retiring Exchange Web Services in Exchange Online on October 1, 2026. Older applications and email clients that rely on EWS may gradually lose access to Microsoft 365 email, calendar, and contact services.

Full Description

What Is Exchange Web Services? 

Exchange Web Services, commonly called EWS, is an older interface that applications and email clients use to access Microsoft 365 mailboxes, calendars, contacts, and related information. Microsoft is retiring EWS in Exchange Online in favor of newer Microsoft interfaces, including Microsoft Graph. 

As Microsoft retires EWS: 

• Legacy email clients that depend on EWS may no longer connect to Microsoft 365 mailboxes. 
• Some third-party applications and synchronization utilities may stop working. 
• Custom scripts and departmental applications that use EWS will need to move to a supported Microsoft interface. 

When Is This Happening? 

Microsoft will begin retiring EWS in Exchange Online on October 1, 2026. Impacts may begin in October 2026 and continue as Microsoft rolls out the change. All applications using EWS will stop working April 2027. Departments should review affected applications before this date. 

Who May Be Affected? 

Most Users Are Not Expected to Be Affected 

You are generally not expected to be affected if you use a current version of: 

• Outlook for Windows 
• Outlook for Mac 
• Outlook on the web 
• Outlook Mobile for iOS or Android 
• Microsoft Outlook included with Microsoft 365 Apps 

These applications use Microsoft's current connection and authentication methods and are expected to continue working after EWS is retired. 

You May Be Affected If You Use 

• Legacy Outlook for Mac 
• An older or unsupported version of Apple Mail 
• An older email or calendar application 
• A device running an unsupported operating system 
• A third-party application that has not been updated recently 
• A calendar or contact synchronization utility 
• A custom script or application that uses EWS 
• Departmental software that connects directly to Exchange Online 

Legacy Outlook for Mac 

Legacy Outlook for Mac uses EWS to connect to Exchange Online. Microsoft states that it will stop working with Exchange Online mailboxes beginning in October 2026. 

If you are using Legacy Outlook for Mac: 

1. Open Outlook. 
2. Turn off the Legacy Outlook switch to move to the current Outlook for Mac experience. 
3. If the switch is unavailable, select Help > Check for Updates. 
4. Install the latest available version of Outlook. 

You may also install the current version through the Mac App Store or the Microsoft 365 portal. 

For additional information, see End of support for Legacy Outlook for Mac. 

Apple Mail and Other Third-Party Applications 

Some versions and configurations of Apple Mail may be affected by EWS retirement. William & Mary users who use Apple Mail should: 

• Keep macOS and Apple Mail fully updated. 
• Install operating system and application updates when available. 
• Reauthorize the account if prompted to use a newer Microsoft sign-in method. 
• Be prepared to switch to Microsoft Outlook if connectivity problems occur. 

Current third-party applications may continue to work if they support Microsoft's current authentication and connection methods. However, compatibility depends on the application and its vendor.  William & Mary IT may recommend using a supported version of Outlook rather than troubleshooting an unsupported third-party email application. 

Personal Devices 

If you use a personal Mac, Windows computer, iPhone, iPad, Android device, or other device to access your William & Mary email: 

• Keep the operating system fully updated. 
• Use a current version of your email and calendar application. 
• Use Microsoft Outlook whenever possible. 
• Replace devices that can no longer run supported software. 
• Use Outlook on the web if your desktop or mobile application stops connecting. 

Older devices that no longer receive manufacturer or operating system updates may be at greater risk of losing email or calendar connectivity. 

Departmental and Custom Applications 

Some departmental software may use EWS to access mailboxes, calendars, or contacts. 

Potentially affected systems may include: 

• Scheduling and room-management software 
• CRM systems 
• Calendar synchronization tools 
• Automated mailbox-processing applications 
• Custom-developed applications and scripts 
• Multifunction devices that integrate with Exchange 
• Applications that monitor or process shared mailboxes 

Departments should contact Information Technology if they manage an application that connects directly to Exchange Online.  When contacting IT, include: 

• Application or service name 
• Vendor name 
• Application owner or departmental contact 
• Purpose of the Exchange connection 
• Mailbox or calendar being accessed 
• Authentication method, if known 
• Any references to EWS, the EWS Managed API, or Exchange SOAP endpoints 

Known Affected Applications and Services 

Information Technology has identified several applications or application registrations for additional review, including Apple Mail for Mac, departmental managed-email services, RoomView, and Crestron scheduling devices. Identification does not necessarily mean that a service will stop working. Each dependency must be evaluated individually. 

Application or service and its current guidance 

Application or service	Current guidance
Current Microsoft Outlook clients	Expected to continue working
Outlook on the web	Expected to continue working
Outlook Mobile	Expected to continue working
Legacy Outlook for Mac	Must move to the current Outlook for Mac experience
Apple Mail for Mac	Keep updated; compatibility is being evaluated
Custom EWS scripts and integrations	Must be reviewed and migrated to a supported interface
Scheduling and room-management integrations	Requires verification by IT or the application owner
Linux Mail Applications i.e. ThunderBird	Move to the current supported Outlook client for web or desktop
3rd Party Mail and Calendar Tools	Move to the current supported Outlook client for web or desktop
Department application integration with email or calendar	Contact vendor to determine if EWS is used

This table may be updated as William & Mary completes additional application and vendor reviews. 

How to Check Your Email Application 

How to Check Your Email Applications on each device 

Outlook for Windows  In Outlook, select File > Office Account > About Outlook to view the installed version.  Install available Microsoft 365 Apps updates.

Outlook for Mac  Open Outlook and determine whether a Legacy Outlook switch is enabled.  If you are using Legacy Outlook, turn off the switch. If the option is unavailable, select Help > Check for Updates and install the latest version.

Apple Mail  From the Apple menu, select About This Mac and verify that the Mac is running a supported version of macOS. Install all available macOS updates, which include updates for Apple Mail.

Web Browser  Sign in to Outlook on the web to confirm that your William & Mary mailbox is available. If Outlook on the web works but a desktop or mobile application does not, include that information when contacting the Technology Support Center.

Frequently Asked Questions 

Frequently Asked Questions

Will My Email Stop Working?  Most users should not experience a change if they already use a current, supported version of Microsoft Outlook.  Users of Legacy Outlook for Mac, older third-party applications, unsupported devices, or EWS-dependent integrations may experience disruptions.

Is Outlook on the Web Affected?  Outlook on the web is expected to continue working after EWS retirement.

Is the Current Outlook for Mac Affected?  The current Outlook for Mac is supported. Legacy Outlook for Mac uses EWS and will stop working with Exchange Online mailboxes beginning in October 2026.

Is Outlook Mobile Affected?  Current versions of Outlook Mobile use Microsoft's current connection methods and are expected to continue working.

What About Apple Mail?  Some versions and configurations of Apple Mail may be affected.  Keep macOS fully updated. If Apple Mail stops connecting, use Outlook for Mac or Outlook on the web and contact the Technology Support Center.

What If I Use Another Third-Party Email Application?  Contact the application's vendor to confirm that the current version supports Microsoft 365 without using EWS. William & Mary IT may recommend moving to Microsoft Outlook if the application is unsupported or cannot connect using Microsoft's current methods.

Have a Departmental Application That Connects to Exchange. What Should I Do?  Contact the Technology Support Center or your departmental IT support provider. Include the application name, vendor, departmental owner, mailboxes or calendars accessed, and any available technical documentation.

Additional Resources 

• End of support for Legacy Outlook for Mac 
• Outlook on the web 

If you need assistance, please contact the Technology Support Center at [[support]], 757-221-HELP, or submit a ticket at gethelp.wm.edu.