SMTP
The protocol that delivers email between mail servers.
Simple Mail Transfer Protocol is the standard for sending email. Most providers offer both an SMTP relay and an HTTP API. SMTP is convenient when migrating from a self-hosted setup; HTTP APIs are easier to debug and authenticate.
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 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.