@sahan-sac/email-kit

Transactional email for server apps, framework-agnostic:

• Providers with fallback: Resend over HTTPS and any SMTP relay (Brevo by default) through nodemailer, tried in order; a failure about the message itself is not retried elsewhere. A capture provider keeps mail in memory for tests and is refused in production.
• Guards: CR/LF header injection, address and mailbox validation, http(s) only links, recipient, subject and body limits (prepareMessage).
• Env schema: spread emailEnvSchema.shape into your own zod schema, or call parseEmailEnv(process.env). emailProductionProblems(env) lists what must stop a production start.
• Health (emailHealth) for a settings screen: provider order, what is missing, never a secret. Brevo diagnostics (runBrevoDiagnostics) for "accepted but never delivered".
• Layout (renderEmail(subject, content, { brand, copy })): one escaped HTML and text layout with a button and a secondary link. copy: true makes the redacted version for CC: every link left out, with a note saying why. copyRecipients(cc, exclude) picks who gets it.

Templates, the audit store and when to send stay in your app.

Environment

| Variable | Used for | | --- | --- | | EMAIL_PROVIDER | auto (default: every configured provider, Resend first), resend, brevo-smtp, or capture (tests only). | | RESEND_API_KEY, RESEND_SENDER_EMAIL, RESEND_SENDER_NAME | Resend. | | EMAIL_HOST, EMAIL_PORT, EMAIL_USE_TLS, EMAIL_HOST_USER, EMAIL_HOST_PASSWORD, DEFAULT_FROM_EMAIL (or EMAIL_SENDER_USER) | SMTP. Port 465 is implicit TLS; other ports must upgrade with STARTTLS while EMAIL_USE_TLS is on. | | EMAIL_BREVO_API_KEY | Read-only Brevo diagnostics. | | EMAIL_CC | Comma-separated addresses for redacted copies of account emails. |

Use

import { createEmailService, emailConfigFromEnv, parseEmailEnv, providerOrder } from "@sahan-sac/email-kit";
import { createResendProvider } from "@sahan-sac/email-kit/providers/resend"; // needs `resend`
// SMTP: createSmtpProvider from "@sahan-sac/email-kit/providers/brevo-smtp" (needs `nodemailer`)

const env = parseEmailEnv(process.env);
const config = emailConfigFromEnv(env);
const providers = providerOrder(config, process.env.NODE_ENV === "production").flatMap((name) =>
  name === "resend" && config.resend ? [createResendProvider(config.resend)] : []
);
const mail = createEmailService({ providers, audit: async (event) => myAuditLog.write(event) });
await mail.send({ to: "[email protected]", subject: "Hi", html: "<p>Hi</p>", text: "Hi", category: "test" });