Scenario
The Exclaimer Outlook Add-in is missing from the Outlook ribbon, appears grayed out, or does not respond, even though you deployed it through Centralized Deployment in the Microsoft 365 Integrated Apps portal.
This issue can occur in the following situations:
- You set the Add-in deployment method to Optional or Available instead of Default.
- You disabled Exchange Web Services (EWS) for the tenant.
Reason
Microsoft is retiring Exchange Web Services (EWS) in Exchange Online. Microsoft plans to begin phased disablement on October 1, 2026, with permanent retirement scheduled for April 1, 2027.
The Exclaimer Outlook Add-in uses modern authentication and does not rely on EWS to insert signatures. However, Microsoft's Centralized Deployment mechanism, which delivers and loads centrally deployed Add-ins, currently requires EWS to remain enabled at the tenant level.
As a result, disabling EWS can prevent centrally deployed Add-ins from loading. This limitation affects vendors that use Microsoft's Centralized Deployment mechanism, not just Exclaimer.
Microsoft has documented two related known issues that can cause the Add-in to behave this way:
- Add-ins deployed with the Optional or Available deployment method may not appear for users.
- Changes to Exchange authentication, including disabling EWS, can cause Add-ins to intermittently fail to load.
Microsoft has marked the EWS-related Centralized Deployment issue as mitigated on its side.
Resolution
If the deployment method causes the issue
Review the Exclaimer Add-in deployment settings in the Microsoft 365 Integrated Apps portal. Set the deployment method to Default instead of Optional or Available.
If EWS is disabled on the tenant
A tenant administrator can re-enable EWS by following these steps:
- Open Exchange Online PowerShell and connect using Global Administrator credentials.
-
Run the following command:
Set-OrganizationConfig -EwsEnabled:$true - Restart Outlook and verify that the Exclaimer Add-in appears in the ribbon.
We recommend:
Update all users to Build 19725.20000 or later before October 2026.
Microsoft currently offers this build on the Current Channel, Monthly Enterprise Channel, and Semi-Annual Enterprise Channel.
Classic Outlook builds 19725.20000 and later support Microsoft's baseline security mode and no longer depends on EWS for Add-in functionality.
For troubleshooting help, see the Troubleshooting section of our interactive guide.
If you need to raise a support ticket, run our diagnostic PowerShell script to help the Support team check your Outlook and Exclaimer Add-In setup. The script safely collects technical details, such as Outlook version, Add-In status, and connectivity, without accessing personal data or emails, enabling faster troubleshooting.
To run the script:
- Launch Windows PowerShell. Administrator privileges are optional but recommended.
-
Enter the following command:
Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass; Invoke-WebRequest -Uri "https://raw.githubusercontent.com/exclaimerltd/Internal-Support-Scripts/master/AddInChecks.ps1" -OutFile "$env:TEMP\AddInChecks.ps1"; & "$env:TEMP\AddInChecks.ps1"
- Follow the on-screen prompts.
-
When complete, a report named AddInChecks.html will be generated.
NOTE: Report Location:
By default: C:\Users\<YourUser>\Downloads\AddInChecks.html
Fallback (if Downloads is unavailable): C:\Temp\AddInChecks.htmlAttach the generated file to your Support ticket to allow the Support team to review your configuration.
If your Support request concerns authentication, include an export of the affected user's Entra ID sign-in logs with your Support ticket.
To export the logs:
- Sign in to the Microsoft Entra admin centre.
- Navigate to Monitoring & health > Sign-in logs.
- On the Interactive sign-ins tab, filter by the affected user's UPN and the date range covering the issue, then export as CSV.
- Switch to the Non-interactive sign-ins tab, apply the same filter, and export as CSV.
- Attach both CSV files to your support ticket.