EWS Deprecation Is Here — Is Your Exchange Online Environment Ready?

After years of discussion and preparation, Exchange Web Services (EWS) in Exchange Online is entering its final phase.

Microsoft has started the phased disablement of EWS from October 2026, with EWS scheduled to be fully disabled in Exchange Online in April 2027.

For many organizations, this isn't new. Those that started preparing early have already been identifying applications using EWS to access Exchange Online, working with application and business owners, engaging vendors and moving supported workloads towards Microsoft Graph.

But there may still be work to do.

Finding the Remaining Dependencies

From my experience with large enterprise messaging environments, knowing that a technology is being retired is the easy part.

EWS has been part of the Exchange ecosystem since Exchange Server 2007, and many applications have used it over the years.

For this retirement, the focus is specifically on applications using EWS to access Exchange Online.

Some of those applications may already have moved to Microsoft Graph. Others may still be in transition, waiting for application changes or vendor support, particularly where there isn't a straightforward Graph equivalent.

That's why identifying the remaining Exchange Online EWS dependencies is important. Application owners, business stakeholders, messaging teams and vendors may all need to work together to complete the migration.

The Next Few Months Matter

The EWS disablement isn't happening across every tenant at exactly the same time. Microsoft is rolling out the change tenant by tenant, starting with Worldwide (WW) tenants, with other environments following their respective rollout timelines.

If your organization has already started the migration, now is a good time to revisit the landscape.

A few things worth checking:

• Review the EWS Usage Report — identify applications still making EWS calls to Exchange Online.

• Check the Graph migration status — confirm what's already moved and what's still in progress.

• Revisit vendor-blocked applications — check whether vendors now have a migration path or updated support.

• Look for anything missed — older integrations and less-visible applications can easily remain in the environment.

Microsoft also provides migration guidance and tools to help developers assess existing EWS applications and potential Graph migration paths.

If you haven't started yet, start with discovery. Identify the applications, understand why they're using EWS, find the owners and build a migration plan.

The phased rollout through April 2027 provides some time to work through the remaining dependencies, but I wouldn't treat that as time to wait.

I'd treat it as time to finish the job.

One Important Distinction

This retirement applies to EWS in Exchange Online.

EWS isn't being retired from on-premises Exchange Server as part of this change.

Hybrid organizations should therefore look specifically at applications and scenarios interacting with Exchange Online mailboxes, including any relevant hybrid or cross-organization dependencies.

Final Thoughts

EWS has served the Exchange ecosystem for almost two decades.

Its retirement is another reminder that legacy dependencies can remain long after the technology landscape around them has changed.

Having worked through these kinds of enterprise messaging transitions, one thing continues to stand out for me:

The technology change is often the easier part. Finding the dependencies, getting the right people involved and moving every application safely is where the real work happens.

If you're already on the EWS migration journey, now is the time to close the remaining gaps.

If you haven't started, now is the time to understand your landscape.

References

Microsoft Exchange Team — EWS Deprecation Is Here – What This Means To You

Microsoft Learn — Deprecation of Exchange Web Services in Exchange Online

Microsoft Learn — Exchange Web Services (EWS) Usage Report

Microsoft Graph — Migrate Exchange Web Services (EWS) apps to Microsoft Graph

Microsoft Exchange Team — Impact of Exchange Online EWS Deprecation on Hybrid Rich Coexistence and Cross-org Sharing