Bottom Line
On October 1, 2026, Microsoft will shut down Exchange Web Services for Exchange Online. If your backup vendor hasn’t migrated to the Graph API by then, your Exchange backups will stop working.
That’s not a gradual deprecation. It’s a hard cutoff. EWS endpoints will stop responding, and any backup product still calling them will lose the ability to back up or restore your Exchange data—emails, calendars, contacts, and tasks.
What Is EWS And Why Does It Matter?
Exchange Web Services was the standard method for third-party applications to interact with Exchange Online data for over a decade. It was well-documented, stable, and reliable. The Graph API is Microsoft’s modern replacement—broader in scope and Microsoft’s clear strategic direction—but migrating from EWS to Graph is not a simple swap.
The two APIs handle Exchange data differently. Migration requires genuine engineering work and introduces architectural changes that can affect backup behaviour, speed, and feature parity. That’s why, despite years of warning, some vendors are still running on EWS for some or all of their Exchange operations.
If your vendor is one of them, you have roughly six months to find out and plan accordingly.
Which Vendors Are Affected?
After retirement, EWS endpoints will stop functioning for Exchange Online. Any backup product still using EWS to access Exchange data will lose the ability to back up or restore Exchange content.
This does not affect on-premises Exchange Server (EWS will continue to work for on-prem deployments). It specifically impacts cloud-based Exchange Online access through EWS.
Which Backup Vendors Are Affected?
This is the question every IT team running M365 backup should be asking right now—and the answer isn’t as straightforward as it should be.
Some vendors migrated to the Graph API years ago and will be completely unaffected. Others still use EWS for some or all of their Exchange operations. The problem is that most vendors don’t make this information easy to find.
In our testing of 12 M365 backup products at BackupVerdict, we’re now reaching out to each vendor to confirm whether they use EWS, Graph API, or a combination for Exchange backup and restore operations. We’ll update our individual reviews as responses come in.
What we know so far: Veeam has confirmed they do not use EWS and are fully on Graph API. For all other vendors, we recommend checking directly—don’t assume.
Four Questions To Ask Your Vendor Before October
- Does your product use EWS or the Graph API for Exchange Online backup and restore?
- If EWS, what is your confirmed migration timeline to Graph API?
- Will the migration affect any existing features, backup speeds, or restore capabilities?
- Do we need to update any application permissions or configurations on our end?
The first question is the only one that matters initially. If the answer is “Graph API only,” you’re clear. If EWS is involved in any part of the pipeline, you need a confirmed migration plan with specific dates—not a vague commitment to “upgrade soon.”
Five Things That Can Go Wrong During Migration
Even vendors with a solid migration plan will face technical trade-offs. Here’s what to watch for:
Feature gaps. Some operations that were straightforward in EWS require different approaches in Graph. Vendors migrating late may temporarily lose or change certain capabilities. Ask specifically about any features you depend on.
Speed changes. Graph API has its own rate limiting and throttling behaviour—which Microsoft is now enforcing more aggressively (see our separate article on the March 2026 API throttling enforcement). Vendors switching from EWS may see changes in backup or restore speeds, particularly for large mailboxes.
Permission changes. Graph API uses a different permission model. You may need to re-authorise your backup application or update app registrations in Azure AD to grant the correct Graph API permissions. This is admin work on your end, not just the vendor’s.
Restore behaviour. How data is written back to Exchange can differ between EWS and Graph. Items that restored cleanly under EWS may behave differently under Graph. Test restores after your vendor migrates—don’t just take their word that everything works.
Quiet failures. The worst-case scenario isn’t a dramatic failure on October 1. It’s discovering in November that your Exchange backups silently stopped running weeks ago because the vendor’s migration was incomplete. Check your backup health dashboards proactively around the cutoff date.
The Bigger Picture
The EWS retirement is the second major change to hit the M365 backup market this year. Earlier this month, Microsoft also began enforcing restrictions on the use of multiple application registrations to circumvent API rate limits—a practice that was inflating backup speed claims across the industry.
Together, these changes are reshaping the vendor landscape. Products built on modern, Graph API-native architectures are unaffected. Products still relying on legacy access methods or multi-application workarounds face forced migration under time pressure—and their customers bear the operational risk.
The action for IT teams is clear: confirm your vendor’s EWS status this month. Test after any migration. And if you’re evaluating new vendors, make Graph API readiness a non-negotiable requirement.
BackupVerdict tests and reviews M365 and Google Workspace backup solutions with hands-on methodology. For our full reviews and comparison guides, visit backupverdict.com.