This address is part of Yealink, a well-known company that makes VoIP phones and video conferencing equipment. The subdomain is set up as a content delivery resource — basically a server meant to store and serve files like images or software updates. The security measures are solid: HTTPS is enforced, the connection uses modern encryption, and Google sees no threats associated with it.
What stands out is that the site itself is currently broken — it returns a 400 error, meaning the server doesn't understand the request. That's not a scam signal per se, but it does mean this particular URL isn't serving anything useful right now. There's also no contact info, about page, or legal docs, which is normal for a backend server but means you can't get support here.
So is cdn-us-resource.ymcs.yealink.com safe? Yes, in the sense that there's no evidence of malware or phishing. But is it a scam? No — it's simply a misconfigured resource server from a legitimate company. If you're a developer integrating Yealink products, you don't need to worry about this domain. If you stumbled across it and expected a working website, you won't find one.