However, those who use third-party services or have built in-house email integrations that rely on EWS will have to migrate, he noted, adding, “you could experience some disruption.”
This is a good reminder that cloud services are managed at scale for the benefit of the provider, Roberts said, and this is part of Microsoft’s push to eliminate technical debt. “In this case, eight years is a long time,” he said. “Sysadmins should pay attention, understand where vendors are going, and mitigate with proactive updates.”
Microsoft’s plan is to disable EWS tenant-by-tenant using the EWSEnabled property, a setting in Exchange Online that essentially works as an on-off switch to control access to EWS. The property supports three values: “true” (access allowed), “false” (access denied), and “null” (the default setting today). On October 1, 2026, null values will automatically change to false, meaning EWS will be blocked for all apps.