Classification: Perimeter Defense & Mail Authentication
Status: Implemented & Verified
Executive Summary
This report covers auditing, remediating, and enforcing cryptographic and domain-level email authentication records (SPF, DKIM, and DMARC) across a multi-service custom domain. The objective was resolving silent delivery failures for automated application notifications, aligning third-party transactional mail providers, and enforcing a strict quarantine policy to protect domain reputation against spoofing and phishing attempts.
Threat Model & Problem Statement
When operating self-hosted services alongside third-party transactional email relays and professional mail routing, misaligned authentication headers lead to two major failure modes: