Mailing

Transactional email uses Resend and React Email templates that live next to the feature that sends them. The free template wires the Resend client; packs add the templates and call sites.

Client

// apps/backend/src/libs/email/resend.ts
import { Resend } from "resend";

export const resend = new Resend(process.env.RESEND_API_KEY);

The From address is built from RESEND_FROM_DOMAIN (see app constants). Without RESEND_API_KEY, optional send paths (billing receipts, some notification channels) skip email instead of failing the request. Auth and invitation flows that require email will not work until the key is set.

Environment variables

Variable	Purpose
`RESEND_API_KEY`	Resend API key
`RESEND_FROM_DOMAIN`	Domain used for the From address

Template locations

Templates are React Email components colocated under feature modules, for example:

Email	Typical path
Password reset / changed	`features/auth/modules//emails/.tsx`
Organization invitation	`features/organizations/modules/send-organization-invitation/emails/`
Billing receipt	`features/billing/modules/send-receipt/emails/receipt.tsx`
Admin notification	`features/notifications/.../emails/admin-notification.tsx`

Send sites call resend.emails.send({ from, to, subject, react }) (or HTML) directly from the module. There is no separate email microservice.

Trigger points

Flow	When it sends
Auth	Password reset, email verification (starter-dependent)
Organizations	Invitation email on send / resend
Billing	Receipt after successful payment when Resend is configured
Notifications	Optional email channel when admins target specific users

Frontend links inside emails should use the frontendUrl() helper so paths and query params stay typed against FRONTEND_URL.

Adding a template

Create a React Email component next to the module that will send it
Call resend.emails.send from that module with the component as react
Keep provider-specific HTTP details in libs/email
Document any new env needs in .env.example

Backend