Glossary
Email API
An HTTP interface for sending email from code.
An email API lets applications send mail with an HTTPS request instead of operating an SMTP server: authenticate, POST JSON describing the message, and get back an identifier. The provider handles queueing, retries, delivery, bounces, and events.
What separates good email APIs from thin SMTP wrappers: idempotent sends, structured errors with request IDs, sandbox/test modes, event timelines per message, and webhooks that retry. Calder's reference lives under Documentation.
In Calder: Calder API reference