Outlook Addin development - Sideloading rejected by exchange

Question

We are trying to develop outlook Addin . Here is official documentation.
Development is straightforward. Installation also can be done in Exchange by the exchange administrator.

The problem is testing during the development. When using the this guide uploaded the manifest in outlook, I got error - Sideloading rejected by exchange.

My exchange administrator does not have any clue, how to get rid of this and developers are asking how to test the developed code? Can someone tell how to do the development of addin and test, without repeatedly sharing manifest with exchange administrator? As, in an enterprise, uploading manifest in exchange is a 2-3 weeks process following change request process.

• Is there any other way than Sideloading to test the add in ?
• Is there any configuration available for exchange administrator, to allow sideloading for a specific group of developers?

Answer 1

I also got this issue trying to side-load using the manifest.xml created by the generator. I think there is an issue with the template. It works for me when I use a sample from the Office-Add-in-samples repo. The one I tried specifically was the outlook-set-signature sample.

Answer 2

I had the same issue with Exchange rejecting sideloading. The error I received was:

-Error sideloading!-- Error: Command failed: npx @microsoft/teamsapp-cli install --xml-path (×) Error: M365.PackageServiceError: Request failed with status code 400 (tracingId:...) BadRequest: Sideloading rejected by Exchange

In my case the issue was caused by the closing curly brace } in some URLs, which invalidated the manifest.

I ran npm run validate to check the manifest and found the following errors:

Error #1:

XML Schema Validation Error: The 'DefaultValue' attribute is invalid. The value 'https://localhost:**3000}assets**/icon-16.png' is not a valid URL.

Error #2:

XML Schema Violation: The manifest does not adhere to the required XML schema definitions.

After correcting the issue, the validation result showed: The manifest is valid.

This resolved the sideloading issue, and I was able to proceed successfully.