Skype for Business Server hybrid: ready for the EWS shutdown?

Short answer: Skype for Business Server in hybrid with Exchange Online still reads calendars and contacts over EWS; Microsoft says a Graph update is upcoming. Keep the IDs from Microsoft's page on the allow list until that update is installed.

✖ Still needs EWS · vendor statements checked 26 Oct 2026

Deadline: Exchange Online blocks EWS by default from October 2026 (tenants are switched to EwsEnabled False, rollout to late April 2027) and turns it off for good on 1 April 2027, with no exceptions. Exchange Server on-premises is not affected.

Status

Microsoft: Graph update upcoming (Learn "Prepare for EWS retirement"). Uses the OAuth service name plus the Microsoft Office app ID.

App ID in the EWS usage report:

What to do

  1. Follow Microsoft's page for the exact IDs and service names for your topology.
  2. Keep them on the allow list.
  3. Install the Skype for Business Server update with Graph support when it ships.

More than one app? Run the free read-only script: it names every app still calling EWS in your tenant.

Allow-list it safely

Setting EwsAllowedAppIDs replaces the whole list, so adding one ID on its own removes every other app. Read the current list first, then write the merged list:

Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Format-List EwsEnabled,EwsAllowedAppIDs
Set-OrganizationConfig -EwsEnabled $true -EwsAllowedAppIDs "<current IDs>,<new ID>"

Changes to the list take up to 24 hours. A blocked call returns HTTP 403 with the header X-EWS-Policy-Reason. The free script prints the merged command for every app in use (it never runs it).

Sources

MSP or IT partner? The M365 Readiness Pack runs this EWS check, the SMTP AUTH check and SPF/DKIM/DMARC for every domain once per client tenant, and writes a client-ready report with your logo, next steps and an email to send the client. Read-only, works with GDAP.

See the pack (from $49)
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