## Context

The Journal has passkey auth (primary) and magic link login (fallback). Magic
links work in dev (auto-redirect) but in production the link is only logged
to console — users never receive it. No email infrastructure exists.

## Goals / Non-Goals

**Goals:**
- Actually deliver magic link emails in production
- Send a welcome email after registration
- Provider-agnostic email interface (easy to swap providers)
- HTML templates with plain-text fallback
- Easy to add new email types in the future (just add a template + call)
- Dev mode: still log to console / return devLink (no real emails)

**Non-Goals:**
- Marketing emails or newsletters
- Email preferences / unsubscribe (only transactional)
- Inline CSS / complex email layouts (keep it simple text-focused)
- Queuing or retry logic (provider handles delivery)

## Decisions

### D1: Resend as email provider

Use [Resend](https://resend.com) — simple API, generous free tier (3k
emails/month), good developer experience. Single dependency: `resend` npm
package.

**Alternative considered**: Nodemailer + SMTP. More complex setup, requires
SMTP server. Resend is simpler for a small project.

**Alternative considered**: Postmark. Similar to Resend but less ergonomic API.

### D2: Email module in apps/journal/app/lib/email.server.ts

Not a shared package — only the Journal sends emails. Keep it simple:
- `sendEmail(to, subject, html, text)` — low-level sender
- `sendMagicLink(email, link)` — template wrapper
- `sendWelcome(email, username)` — template wrapper

In dev mode, `sendEmail` logs to console instead of calling Resend.

### D3: Inline HTML templates

Simple functions returning HTML strings. No template engine. Each email type
is a function: `magicLinkTemplate(link)`, `welcomeTemplate(username)`. Plain
text generated by stripping tags.

### D4: Sender domain: noreply@trails.cool

Requires DNS verification (DKIM/SPF records) with Resend. Add TXT records via
Terraform or manually in Hetzner DNS.

## Risks / Trade-offs

- **Resend vendor lock-in** → Low risk. The `sendEmail` wrapper abstracts it.
  Swapping to nodemailer later is a one-file change.
- **DNS verification required** → Must add DKIM/SPF records before emails work.
  Can use Resend's test domain initially.
- **Free tier limits** → 3k/month is plenty for <100 users.