This rule flags inbound messages where the sender originates from Domains By Proxy (domainsbyproxy.com), a domain privacy service used to obscure ownership. The condition is a simple domain check: type.inbound and sender.email.domain.root_domain == 'domainsbyproxy.com'. Purpose is to identify potential abuse of privacy services in support of spam, credential phishing, or business email compromise (BEC). Detection methods rely on header analysis (inspection of email headers such as Received and From) and sender analysis (deriving the root domain from the sender’s email). As a standalone signal, it is best used to augment broader fraud detection, not as conclusive proof of malicious activity. Typical workflow would entail correlating with authentication results (SPF/DKIM/DMARC), IP reputation, link/attachment analysis, and user reporting to reduce false positives and improve triage efficiency. Consider enabling automated follow-ups such as additional scrutiny, quarantine, or tagging for security review when Domains By Proxy is detected, especially in conjunction with other suspicious indicators. Be aware that legitimate use of privacy services exists, so risk-based handling and potential allowlisting for trusted domains may be warranted to avoid false positives and operational disruption.