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Microsoft has announced the End-of-Service (EOS) for Exchange Web Services (EWS) in Exchange Online, effective October 1, 2026. This move impacts numerous applications, plugins, and migration tools that rely on EWS for connectivity.
Why This Matters
- Many Outlook plugins and third-party apps depend on EWS.
- On-premise Exchange migrations to Exchange Online currently use EWS.
- Classic Outlook employs a mix of MAPI and EWS for Exchange Online connectivity.
Microsoft has been phasing out legacy protocols, starting with the removal of Basic Authentication. Now, EWS joins the deprecated list, pushing organizations toward Modern Authentication (OAuth 2.0) and Microsoft Graph API.
Official Microsoft Announcements
You Should Know: How to Prepare for EWS Deprecation
1. Identify EWS-Dependent Applications
Use Exchange Online PowerShell to detect EWS usage:
Get-ConnectionByClientTypeDetailReport -StartDate (Get-Date).AddDays(-30) -EndDate (Get-Date) | Where-Object {$_.ClientType -like "EWS"} | Export-Csv EWS_Usage_Report.csv
2. Migrate to Microsoft Graph API
Replace EWS calls with Graph API endpoints. Example:
curl -X GET "https://graph.microsoft.com/v1.0/me/messages" -H "Authorization: Bearer {access_token}"
3. Update Outlook & Third-Party Plugins
Ensure all plugins use REST APIs instead of EWS.
4. Monitor Exchange Online Logs
Use Azure Sentinel or Microsoft Defender for Office 365 to track EWS connections:
Get-MailTrafficATPReport -StartDate (Get-Date).AddDays(-30) -EndDate (Get-Date) -ActionType Blocked | Format-Table
5. Test Modern Authentication (OAuth 2.0)
Enable and enforce OAuth for Exchange Online:
Set-OrganizationConfig -OAuth2ClientProfileEnabled $true
What Undercode Say
Microsoft’s deprecation of EWS is part of a broader push toward secure, modern authentication. Organizations must audit their Exchange Online integrations and migrate to Graph API or REST-based alternatives.
Key Linux & Windows Commands for Migration
- Check Active EWS Sessions (Linux):
grep "EWS" /var/log/exchange/conn.log
- Force OAuth in Outlook (Windows):
Set-OutlookProvider -Identity ExchangeOnline -UseOAuth $true
- Block Legacy Auth via Conditional Access (Azure):
New-ConditionalAccessPolicy -Name "Block Legacy Auth" -State Enabled -Conditions @{ClientAppTypes = @("ExchangeActiveSync", "Other")} -GrantControls @{Operator = "OR"; Controls = @("Block")}
Expected Output:
A structured migration plan ensuring zero reliance on EWS by 2026, leveraging Microsoft Graph API and OAuth 2.0 for secure, future-proof Exchange Online integrations.
References:
Reported By: Charlescrampton Since – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
