← 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 The Myth of Content as Primary Deliverability Variable Many email marketers believe that content is the primary driver of inbox placement. The infrastructure evidence points elsewhere. Architecture Scope Fleet Scale High-Volume Infrastructure […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary GDPR-Compliant Email Operations for European Senders Production engineering runbook on GDPR-Compliant Email Operations for European Senders: telemetry signals, MTA queue architecture, and deliverability guidelines. 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 Apple MPP and Engagement Metric Reliability in 2026: What iOS 18 Changed and What Operators Should Track Instead Apple Mail Privacy Protection now drives roughly half of all reported email opens, and […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Why Bounce Handling Is a Shared Responsibility: MTA and Application Bounce processing requires coordination between the MTA and the sending application. 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 The Role of PTR Records in Modern Deliverability PTR records (reverse DNS) were once essential for inbox placement. They remain a trust signal in 2022, but their role has shifted. Architecture Scope […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary SMTP Relay vs MTA Ownership: The Operational Difference Using a third-party SMTP relay and owning your MTA infrastructure are fundamentally different operational arrangements. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Why Email Volume Doesn't Explain Deliverability Volume is often blamed for deliverability problems. In almost every case, it is not the volume itself but the quality of the signals accompanying that… Architecture […]