stop IIS from changing headers

I'm using laravel with the Barryvd/cors package. The package makes sure all my api calls have the correct cors headers set up via middleware.

Locally this works the way it should, but when using IIS to host the website it does not send the headers at all.

I've tried to add it in my server config manually but then it still misses other headers.

Is IIS overwriting my headers?

via Chebli Mohamed