Service Update
| By | October 1st, 2026 |
| Product(s) |
Email Security - MX,
Email Security Cloud Integrated Sync & Recover, Continuity for Office 365, Mimecast Synchronization Engine (MSE), Simply Migrate. |
| Who's affected | Administrators |
Overview
Microsoft is permanently retiring Exchange Web Services (EWS) for Exchange Online. This is a Microsoft-driven, industry-wide change that affects every software vendor using EWS to connect to Microsoft 365. It does not affect On-Premises Exchange environments.
Several Mimecast services currently depend on EWS, and will be impacted from October 2026.
What's changing
Key dates
- October 1st, 2026: EWS begins being disabled by default across Exchange Online tenants. Affected services will stop functioning for any tenant where EWS has been disabled.
- April 1st, 2027: Full and permanent shutdown of EWS for Exchange Online. No exceptions and no re-enablement after this date.
Services being permanently discontinued
(no direct replacement available after October 2026 / April 2027, depending on when EWS is disabled for your Microsoft tenant)
| Service | Status |
| Mailbox Storage Management (MSE) | Permanently discontinued. No replacement available. |
| Managed Folders (MSE) | Permanently discontinued. No replacement available. |
| Simply Migrate - Archive Mailbox | Permanently discontinued. No replacement available. |
Services that might be temporarily paused based on circumstances
| Service | Status |
|
Sync & Recover - Restore function (Email Security - MX and Cloud Integrated) |
Can continue to use Restore until EWS is no longer supported
by Microsoft. Extension until April 1st, 2027 can be given
by
Microsoft
if you notify them. We are waiting on Graph API to allow us to replicate this functionality, which is not available today. If we need to temporarily pause the service, a manual workaround through PST / EML export will be available as an interim workaround. |
| Simply Migrate - Legal Hold (Recovery Hold) | Temporarily paused pending Microsoft's replacement API reaching general availability. |
Services requiring migration required before October 2026
Individual migration guides will be published for each service, ahead of the recommended migration window.
| Service | Notes |
| Threat Remediation |
A Graph API migration path is available. You should migrate to the new Graph API connector, by following the
instructions at
Migrating Server Connectors. Additional benefits of switching include improved remediation speed and performance through a more secure connection. |
| Sync & Recover - Sync (Email Security - MX) | New Graph API connector planned for release between April and May 2026. Migration guide will be provided. |
| Continuity for Office 365 (Event Monitor) | New Graph API connector planned in the coming months. A migration guide will be provided. |
| Mailbox Folder Replication (MSE) | Being rebuilt as a new agentless, UI-based solution. Availability date to follow. |
| Calendar Replication (MSE) | Being rebuilt as a new agentless, UI-based solution. Availability date to follow. |
Recommended actions
-
If you use a discontinued service (Mailbox Storage Management, Managed Folders, Simply Migrate Archive Mailbox):
Export any data you need to retain before September 2026. Do not rely on the April 2027 hard deadline. Microsoft's phased disablement begins in October 2026 and the timing for individual tenants is outside Mimecast's control. Detailed export guidance will be published ahead of the deadline. -
If you use a service that might get paused (Sync & Recover Restore):
Ask Microsoft for an extension to use EWS-reliant services until April 1st, 2027. Tenants can temporarily enable EWS between October 2026 and April 2027 by configuring an AppID Allow List and settingEWSEnabled=True. This will allow you to continue to use these services for longer. After doing this, follow Mimecast updates. -
If you use a migration-required service:
- Threat Remediation: Migrate to the new Graph API connector, by following the instructions at Migrating Server Connectors.
- Other services: No immediate action required. Watch for individual product communications with step-by-step migration guides. The migration to new connectors has a deadline of October 2026.
Full details are available in the EWS Retirement FAQ.
If you have any questions about this change, please contact your Mimecast Customer Success Manager (CSM), Account Executive, or Mimecast Support.
See Also...
- Microsoft Exchange Web Services (EWS) Retirement - Frequently Asked Questions
- Email Security - MX
- Continuity
- Mimecast Synchronization Engine
- Simply Migrate
- Sync & Recover
- Sync & Recover - Overview
- Threat Intelligence & Remediation
- Migrating Server Connectors
Comments
Step by step on how to migrating quide the exixting EWS connector to the new Graph API connector
Hi Thulani Mokoena, many thanks for your feedback.
We’d advise you to read the FAQs at https://mimecastsupport.zendesk.com/hc/en-us/articles/50418638259603-Microsoft-Exchange-Web-Services-EWS-Retirement-Frequently-Asked-Questions which are linked from the Recommended Actions section of this Service Update.
Key information from the FAQs, to answer your question:
”Mimecast is actively preparing service-specific migration guides and customer communications for all affected services. You will receive these ahead of the October 2026 deadline. If you have not heard from us by April 2026 and believe you are affected, please contact your Mimecast Customer Success Manager (CSM), Account Executive, or Mimecast Support.”
Hi Hi Thulani Mokoena,
Please note that we have updated the FAQ with respect to Threat Remediation.
A Graph API migration path is available. You should migrate to the new Graph API connector, by following the instructions at Migrating Server Connectors.
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