← 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 Post-Pandemic Email Volume Spikes: Infrastructure Lessons from 2020-2021 The 2020-2021 period produced sudden, large email volume increases as organisations moved communications online. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary IPv6 for Email Sending: Infrastructure Readiness Assessment IPv6 adoption in email infrastructure is accelerating but uneven. 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 Diagnosing Authentication Drift in Long-Running Infrastructures Authentication configurations degrade over time as domains change, services are added, and DNS records accumulate errors. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary When Cold Email Damages Your Transactional Sender Score Cold email and transactional email sent from the same IP or domain creates reputation cross-contamination that degrades transactional delivery. Architecture Scope Fleet Scale High-Volume […]