API vs SMTP
When to use HTTP API versus SMTP relay.
HTTP APIs return structured errors, support idempotency keys, and integrate with serverless runtimes. SMTP is universal and works with any language. APIs are usually preferred for new code; SMTP is preferred when migrating an existing app or using libraries that already speak SMTP (like Nodemailer or ActionMailer).
reading this as growth and lifecycle teams
Growth work lives or dies on targeting and measurement. What matters is whether behavioral triggers can be built without engineering time, whether the event stream supports attribution past the open, and whether deliverability holds when broadcast volume shares a reputation with product email.
Applied to api vs smtp, that means weighing scheduling, event stream, deliverability, and operating track record ahead of the rest, against behavior-triggered journeys, broadcasts, and winback campaigns measured on revenue.