Due to freely scalable resources in our cloud, we cannot give out the IP address of the cloud. If there is no other way, except whitelisting the IP, then you have to check the access log of the server you want to transfer to and find out the current IP.
Note
It is possible that the IP changes per request - depending on the load on our cloud.
This process should be automated as much as possible, because this IP can change often (per request).