BitTitan MigrationWiz: ready for the EWS shutdown?

Short answer: MigrationWiz still moves Exchange Online mailboxes over EWS. Add your MigrationWiz Modern Authentication app ID to the EWS allow list for the duration of the migration, and finish mailbox migrations into or out of Exchange Online before 1 April 2027.

✖ 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

Still EWS (BitTitan article). The Modern Auth app is the one you registered for MigrationWiz in your tenant.

This vendor registers its own app in each tenant, so the app ID is yours. Find it in the EWS usage report, or run the free script with -ResolveNames.

What to do

  1. Find your MigrationWiz app ID (Entra app registrations, or the script with -ResolveNames).
  2. Add it to the allow list on both source and destination tenants if both are Exchange Online.
  3. Remove it after the project. Schedule the last passes well before 1 April 2027.

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)
Did this fix it?

What's still not working?

Paste the bounce message or describe what happens. We read every report and add fixes for new errors.

Other apps