# ADR 003 — Resend HTTPS transactional email

## Decision

Use a small backend Resend REST adapter over Node 24 native fetch. The application depends on a
narrow email sender port, and the composition root injects either native fetch or a local-only
Mocking Bird transport. The runtime destination is fixed to `https://api.resend.com/emails`.

## Rationale

The planned hosting class can restrict common SMTP ports. HTTPS uses the existing outbound web path
and avoids an SMTP client dependency. A provider-specific adapter is sufficient for one current
integration; no registry or all-provider abstraction is introduced.

## Consequences and prerequisites

Real delivery needs an owner-controlled Resend account, sending-scoped API key, verified sender
domain, and appropriate recipient permissions. These are external release prerequisites and are not
needed for local implementation acceptance. No live send, connectivity check, or automatic retry
occurs during startup or CI. Timeouts may leave delivery status uncertain, so retry behavior
requires a later idempotency decision. See the official
[send-email API](https://resend.com/docs/api-reference/emails/send-email) and
[error reference](https://resend.com/docs/api-reference/errors).