Information Technology Services

Upcoming Microsoft 365 Changes for October 2026

Posted Friday, September 25, 2026

SharePoint OTP Retirement: Changes to Guest Access

To create a more secure file sharing process, Microsoft is changing SharePoint sharing permissions and deprecating legacy one-time passcodes. As a result, MS Teams owners, SharePoint site owners, or OneDrive account holders may receive reports of external members having lost access to their shared data. To resolve this, the owner should re-share any file, folder, or site with the affected guest, after-which guests should regain access to existing shared resources as well. 

Legacy Outlook for Mac Retirement 

Starting October 2026, the legacy Outlook for Mac desktop client will cease working with Exchange Online. Users will need to switch to the New Outlook for Mac desktop client or Outlook on the Web (OWA) to check their email with the Mac OS.

Exchange Web Services (EWS) Retirement

Microsoft will begin retiring Exchange Web Services (EWS) in October 2026, with full retirement completed by April 2027. Applications that rely on EWS to connect to Exchange Online may experience service disruptions through the final retirement in April 2027. Mac Mail (Apple Mail for Mac) is one of the most widely used applications that relies on EWS. Microsoft is working with Apple to support the transition; however, functionality remains dependent on Apple providing the necessary updates. If you are a Mac Mail user and experience issues using the application, it is recommended to switch to the Outlook for Mac desktop client or Outlook on the Web (OWA).