Email Infrastructure

Architecture-level guides for senders past the ESP tier. Stream separation (the most impactful single architecture decision in email — keep marketing complaints from damaging transactional reputation), multi-IP scaling, dedicated domain strategy, the cost comparison at high volume between self-hosted PowerMTA and managed ESPs (the break-even is around 500K/month), and ecommerce-specific infrastructure patterns (abandoned cart isolation, seasonal volume planning, transactional-marketing separation).