If you've come across signalrp2-relayhub-prod-eu03-1.service.signalr.net and wonder whether it's safe, the short answer is that this isn't a website you need to worry about. It's part of Microsoft's Azure SignalR service, which is a legitimate cloud platform used by developers to add real-time features to their apps. The domain resolves to Microsoft's own network, uses a valid Microsoft-issued certificate, and enforces modern encryption. There are no blacklist alerts, no threats from Google, and no signs of malicious activity.
Because this is a backend service endpoint, it returns a 403 Forbidden page when accessed directly — that's expected and not a sign of anything wrong. There's no content to read, no forms to fill out, and nothing to buy. If you're using a product that relies on Azure SignalR, this domain is simply part of the infrastructure working in the background. For developers or anyone checking logs, this is a clean signal. It's not a scam, and there's no reason to be concerned about its legitimacy.