If you are receiving a 401 Unauthorized answer from CaaS even though you did provide the correct API Key using Postman itmight be necessary to check your settings.
The https://<customer>-dev-preview-caas-api.e-spirit.cloud URLs are redirected with a 308 Permant redirect to https://<customer>-dev-caas-api.e-spirit.cloud.
To make ist work again please activate the "Follow Authorization header" option from the settings tab in Postman.
This is option is set to "off" per default.