# Sending email from code

> Treat email as an application dependency. Prefer authenticated APIs over ad-hoc SMTP, separate transactional traffic from marketing reputation, and design for idempotent sends with clear webhook handling.

APIs, SDKs, SMTP boundaries, and the difference between transactional and marketing sends.

## Lessons

- [APIs, SDKs, and the send path](/lessons/apis-sdks-and-sending): How modern ESPs expose sending, and how to pick an interface.
- [Transactional vs marketing email](/lessons/transactional-vs-marketing): Why mixing streams burns reputation and how to split them.

**Canonical:** https://sendemails.dev/courses/sending-from-code

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