Email has the highest ROI of any marketing channel. $36 for every $1 spent. Yet most startups treat it as an afterthought - bulk blasts, no personalization, landing in spam folders.

Email Systems Measure email return and deliverability for the actual audience and attribution window; no universal ROI or inbox delivery guarantee applies. This skill covers transactional email that works, marketing automation that converts, deliverability that reaches inboxes, and the infrastructure decisions that scale. Detailed Guide Read [the detailed guide](references/detailed guide.md) before executing this skill. It retains the complete procedure and reference material. Treat its safety, prerequisites, and validation requirements as mandatory. For focused work, load the relevant sections; for end to end work, read the guide completely. When to Use Use this skill when the request clearly matches the capabilities and patterns described above. Limitations Use this skill only when the task clearly matches the scope described above. Do not treat the output as a substitute for environment specific validation, testing, or expert review. Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing. Example For a password reset, enqueue a short lived opaque reference, fetch the token server side without logging it, and deduplicate provider submission by event ID. A timeout is an unknown send outcome: reconcile before resending; show the same user facing response whether or not the account exists.

email-systems