← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Complaint Rate Spikes: How to Trace Them to Their Source A complaint rate spike is a diagnostic problem, not a mystery. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing Verified […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Separate Transactional and Marketing Domains: Why and How Using the same sending domain for transactional and marketing email creates reputation entanglement that degrades both. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Long-Tail SMTP Errors Operators Overlook Most deliverability attention focuses on 250 OK and major 5XX bounces. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing Verified deliverability standard MTA Engine PowerMTA […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Logging Architecture for Email Infrastructure Email infrastructure generates high-volume logs across multiple systems. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing Verified deliverability standard MTA Engine PowerMTA & Kumo Bare-metal […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary List Validation: Acquisition Time vs Send Time — When to Check Email address validation can happen at acquisition (preventing invalid addresses from entering the list) or at send time (removing them before […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary The Compounding Effect of Small Deliverability Improvements Deliverability is not a single variable to optimise but a system of compounding signals. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing Verified […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Daily Monitoring Checklist for PowerMTA Email Infrastructure Operators A structured daily monitoring checklist for PowerMTA operators: what to check in the accounting log, Postmaster Tools, SNDS, DNSBL status, and… Architecture Scope Fleet […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary ISP-Specific Throttle Behaviour: Why One Size Fits All Fails Gmail, Yahoo, Microsoft, and EU ISPs throttle email differently. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing Verified deliverability standard MTA […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary The Economics of IP Warming: Investment, Timeline, and Return IP warming is a 8-week infrastructure investment with a specific cost structure and a predictable return in throughput capacity and inbox placement. Architecture […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Feedback Loop Data as a Segmentation Tool: Beyond Suppression in 2026 FBL complaint data is typically used only for suppression. In 2026, with Gmail, Yahoo, Microsoft, and Apple offering radically different feedback… […]