Are services IP-addresses static?

I have access to a server behind a corporate firewall. I need a web application on it to talk with The infrastructure department want an IP number to that service, so they can open up a hole in the corporate firewall, so the application is allowed to make the out-going call. If I do an ‘nslookup …’ I can see the receiving IP is - but will it always be so… Is there a range I should know, or can I be certain that the api IP remains static?

No. None of the popular online ocr services offers or guarantees static IP addresses. But there is a workaround: You can run your own server outside your corporate firewall with a fixed IP, and this server does nothing else than forwarding the requests to the cloud api.

Or, for the best privacy and security, use an offline ocr solution.