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Email & Marketing

The platform has two outbound communication concerns: Resend handles account-related security notices and Mailchimp manages the marketing audience. Both are implemented as small edge-compatible clients in src/lib/email/ and src/lib/marketing/. General transactional email — notification emails, digests, share-by-email — is on the roadmap and not yet built.

Overview

Section titled “Overview”

Resend is used today for two security notices only:

  • Email-change notification — when a user confirms a new address, the previous address receives a heads-up. Sent in settings/actions.ts.
  • Account-deletion confirmation — the deleted account’s email receives a notice after deletion completes. Sent in lib/supabase/actions.ts.

Sign-up confirmation goes through Supabase Auth (supabase.auth.signUp), not Resend. Organisation invites are in-app only — the invite email columns were dropped in migration 20260518000003_simplify_org_invites.sql. handleSendPost, sendBatchEmails, resolveUserEmails and hasResolvableEmails are defined in the email library but have no callers in src; share-by-email is not a shipped feature.

Mailchimp receives every new account via subscribeToAudience, called from signup() after a successful auth sign-up. Every new account is subscribed as pending (Mailchimp’s double opt-in state). Failure is caught and logged; signup still succeeds. Mailchimp is the system of record for subscription state: the marketing module only ever adds addresses; unsubscribes are handled by Mailchimp’s own links.

Architecture

Section titled “Architecture”

Resend Client

Section titled “Resend Client”

The Resend client in src/lib/email/client.ts calls the Resend REST API directly with fetch. It reads RESEND_API_KEY and RESEND_SENDER_EMAIL from env.ts. The EMAIL_TEMPLATES registry maps template names to Resend template UUIDs for sendTemplateEmail, though no template sends are called in production today.

Failures throw EmailError. Both live callers use .catch() to log failures without blocking the user-facing action.

Mailchimp Audience Client

Section titled “Mailchimp Audience Client”

src/lib/marketing/mailchimp.ts calls the Mailchimp Marketing API v3 endpoint POST /lists/{audienceId}/members. The datacenter is derived from the key suffix (everything after the last - in MAILCHIMP_API_KEY). The request always sets status pending so Mailchimp sends its own opt-in email. A Member Exists error is treated as a no-op. The call has a 5-second timeout. Missing keys cause fail-fast at startup rather than a runtime error.

Failure Modes & Edge Cases

Section titled “Failure Modes & Edge Cases”
  • Resend failures — both callers wrap sendEmail in .catch() and log the error. The user action (email change, account deletion) proceeds regardless.
  • Mailchimp failures — signup() wraps subscribeToAudience in a try/catch. Failure is logged; signup still succeeds.
  • Member already exists — treated as a no-op, not an error.
  • Preview environments — previews use the live Resend and Mailchimp keys. A sign-up in a preview environment adds a real entry to the Mailchimp audience and sends a real Resend email.
  • Missing configuration — env.ts uses fail-fast validation at build time: a missing API key raises at startup rather than silently failing at runtime.

Operational Notes

Section titled “Operational Notes”

Four environment variables govern both integrations:

Variable Purpose
RESEND_API_KEY Resend API key
RESEND_SENDER_EMAIL From address for all sends
MAILCHIMP_API_KEY Mailchimp API key (datacenter derived from suffix)
MAILCHIMP_AUDIENCE_ID Target audience / list ID

See src/lib/email/index.ts and src/lib/marketing/index.ts for the full exported surface.

Extension Points

Section titled “Extension Points”

When notification emails and other transactional sends ship, they will go through the Resend client. sendTemplateEmail and sendBatchEmails already exist in the library and are ready to be wired up. resolveUserEmails and hasResolvableEmails are helper services for batching emails to sets of users, also unused today.

Section titled “Related Links”