How to properly deal with domain takedown requests?

We keep receiving domain take down requests from our domain registrar for a domain that hosts thousands of clients. The claim is that one URL is being used to capture credentials of the client's customers, but the site is in fact legitimate. They have been a partner with us for almost a decade.

The requests are originating from a 3rd party service provider so I don't know who is telling them the site is illegitimate. The client has not been …

capture claim client clients credentials customers cybersecurity deal domain domain registrar down fact partner registrar requests takedown url