I am facing the following problem and need a correct solution also for SEO purposes.
It happens that our server, which is on a shared hosting, fails and responds with a 503 server error code. What I have done now is setup IIS on another server to allow the requests from that particular domain. It contains 1 page with some details to our customers about the problem. It is some kind of maintenance page.
On the DNS records I now edit the IP to that new server where the maintenance page is located.
This is now visible to our customers but what will Google do now? The 503 server error is now gone and is now a 200 status code because of the new server.
How can I still throw the 503 server error on the new server so that Google knows its a temporarely error?