ZI2 Certified Email Server Attestation Protocol

This document specifies the ZI2 Certified Email Server Attestation Protocol, a mechanism for cryptographic attestation of email origin at the mail server level. Unlike existing email authentication protocols (SPF, DKIM, DMARC), which operate at the domain level, ZI2 Certified operates at the server-instance level, enabling definitive identification of the specific server that dispatched a given email message. The protocol introduces two custom mail headers, a DNS TXT record publication format, a graduated trust model with four levels, and an integration interface for AI-based email classification systems. The protocol operates complementarily to existing email authentication infrastructure and introduces an ARC-Delegated Trust mechanism to preserve origin attestation across legitimate transit modifications.