← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Building a Sending Pool Strategy for Mixed Traffic: 2026 IP Segmentation Patterns That Actually Work Mixing transactional, marketing, and behavioural traffic on a single IP pool conflates reputations that should be kept […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary How Blacklist Operators Identify and List SMTP Sending Infrastructure How Spamhaus, Barracuda, SpamCop and SORBS detect and list sending IPs. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing Verified deliverability […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary The Operational Risk of Single-IP Email Sending Sending all email from a single IP concentrates reputation risk, eliminates warmup headroom, and creates a single point of failure. Architecture Scope Fleet Scale High-Volume […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary What Changes When You Move from Shared to Dedicated Infrastructure The migration from shared relay to dedicated MTA infrastructure changes more than the cost structure. Architecture Scope Fleet Scale High-Volume Infrastructure Production […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Testing Methodologies for Email Infrastructure Pre-production testing for email infrastructure: authentication verification, inbox placement sampling, bounce-path validation, and staged load tests… 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 SMTP Errors Are Not Equal: A Classification Framework Not all SMTP errors require the same operational response. This note provides the classification framework that determines the correct action for each… Architecture Scope […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Designing for Zero Downtime in Email Sending Infrastructure Email infrastructure downtime means undelivered campaigns, delayed transactional messages, and revenue loss. Architecture Scope Fleet Scale High-Volume Infrastructure Production Status 100% Inboxing Verified deliverability […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary Dedicated Infrastructure for High-Stakes Transactional Email Transactional email — OTP codes, password resets, payment confirmations — has zero tolerance for delay or spam-folder placement. 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 How ISP Filtering Evolved: From Content Rules to Reputation Systems Email spam filtering has transformed from keyword blacklists through Bayesian learning to reputation-driven ML classification. Architecture Scope Fleet Scale High-Volume Infrastructure Production […]
← Back to Operational Notes Archive Engineering Operational Note · Published Production Engineering Memo · Technical Architecture · 14 min read Executive Summary The Case for Real-Time Bounce Processing at the MTA Layer Processing bounces in batches — daily or per-campaign — creates a gap during which hard-bounced addresses continue receiving email. Architecture Scope Fleet […]