ServiceNow Outlook Add-in opens in Browser instead of Outlook task pane in Classic Outlook

[tomjuk26]

Hi everyone,

I'm hoping someone has come across this before.

We have deployed the ServiceNow Outlook Add-in and are testing it in Classic Outlook for Windows. The add-in works correctly in Outlook Web, however in Classic Outlook it opens an Edge browser window instead of remaining embedded within the Outlook task pane.

Environment

• ServiceNow Dev Instance: Zurich Patch 10 HF4
• Plugin: ServiceNow Add-Ins for Microsoft 365
  • Version 7.5.1
• Outlook for Microsoft 365
  • Version 2607
  • Build 16.0.20228.20188 (64-bit)
• Microsoft Edge WebView2 Runtime
  • Version 153.0.4234.32

Manifest Configuration

The manifest action is configured as:

<Action xsi:type="ShowTaskpane">

and launches: 

https://%instance%.service-now.com/sn_outlook_addin_load_task_page.do?table=incident

Based on the manifest, I would expect the page to remain inside Outlook.

Expected Behaviour

Clicking "Create an Incident (INC)" should open the ServiceNow page within the Outlook task pane.

Actual Behaviour

Clicking the button launches Edge and opens: 

https://%instance%.service-now.com/sn_outlook_addin_load_task_page.do?table=incident

The page loads and functions correctly in the browser, but it is not embedded within Outlook.

Troubleshooting Already Performed

• Confirmed the add-in works correctly in Outlook Web (OWA).
• Confirmed the page loads successfully in Edge.
• Verified Outlook is fully patched.
• Verified WebView2 is installed.
• Cleared the Outlook add-in cache by deleting: 
  %LOCALAPPDATA%\Microsoft\Office\16.0\Wef
• Confirmed Outlook is using the latest manifest after clearing the cache.
• Reviewed response headers and confirmed CSP includes:
  • frame-ancestors 'self'
    https://outlook.office365.com
    https://outlook.office.com
    https://outlook.cloud.microsoft
• Confirmed there are no X-Frame-Options restrictions preventing embedding.

Additional Finding

While reviewing the ServiceNow Outlook Add-in JavaScript, I found references to:

window.open(...) 

within:

sn_outlook_addin.OutlookAddinOAuthHelper.jsdbx

I'm wondering whether there is logic in the add-in that intentionally launches an external browser window in certain Outlook scenarios.

Questions

1. Is opening Edge expected behaviour for the current ServiceNow Outlook Add-in in Classic Outlook?
2. Has anyone successfully deployed this add-in and had it remain embedded in Classic Outlook?
3. Are there known compatibility issues with recent Outlook builds?
4. Could OAuth authentication be causing the add-in to launch externally rather than remain in the task pane?

Any suggestions or comparisons with similar deployments would be greatly appreciated.

Thanks in advance.