Send email from Express with SNDR.

Express is still the workhorse Node.js framework for API backends; the SDK is a clean fit. The thing every team gets wrong with Express + webhooks: app-level express.json() consumes the request body before your verifier can see the raw bytes, which breaks HMAC. The recipes below mount express.raw() per-route on the webhook handler so verification stays correct without disabling JSON parsing everywhere else.

1. Basic send from a route handler

   Instantiate Sndr once at module scope and reuse the client across requests. Catch SndrError so you can map our error codes to your HTTP responses cleanly.

   // server.ts
   import express from 'express';
   import { Sndr, SndrError } from '@rkiza/sndr';
   
   const app = express();
   app.use(express.json());
   
   const sndr = new Sndr(process.env.SNDR_API_KEY!);
   
   app.post('/api/welcome', async (req, res) => {
     const { email, name } = req.body as { email: string; name: string };
     try {
       const { id } = await sndr.emails.send({
         from: 'hello@yourdomain.com',
         to: email,
         subject: `Welcome, ${name}`,
         html: `<p>Thanks for joining us, ${name}.</p>`,
       });
       res.json({ id });
     } catch (err) {
       if (err instanceof SndrError) {
         res.status(err.status >= 400 && err.status <= 599 ? err.status : 502).json({ error: { code: err.code, message: err.message } });
         return;
       }
       throw err;
     }
   });
   
   app.listen(3000);

2. Webhook receiver — express.raw() per-route

   express.raw({ type: 'application/json' }) is the critical bit. It exposes req.body as a Buffer of the raw bytes so the HMAC verifier can compute over the exact payload SNDR signed. Don't replace it with express.json() — re-serialised JSON breaks the signature.

   import express from 'express';
   import { verifyWebhookSignature } from '@rkiza/sndr';
   import type { WebhookEventPayload } from '@rkiza/sndr';
   
   const app = express();
   app.use(express.json()); // For everything else.
   
   app.post(
     '/webhooks/sndr',
     // Per-route raw body — overrides the app-level json() above for THIS route only.
     express.raw({ type: 'application/json' }),
     (req, res) => {
       const ok = verifyWebhookSignature(
         req.body as Buffer,
         req.header('x-sndr-signature') ?? '',
         process.env.SNDR_WEBHOOK_SECRET!,
       );
       if (!ok) return res.status(400).send('bad signature');
   
       const event = JSON.parse((req.body as Buffer).toString('utf8')) as WebhookEventPayload;
       switch (event.type) {
         case 'email.delivered':
           // event.data.email_id, event.data.to: string[]
           break;
         case 'email.bounced':
           // event.data.email_id, event.data.error
           break;
         case 'email.unsubscribed':
           // event.data.addresses: string[]
           break;
       }
   
       res.status(200).send('ok');
     },
   );

3. Queue + retry (BullMQ)

   Inline sends couple your route latency to the upstream API. A BullMQ worker with autoretry handles transient failures and keeps the request fast. Pair with a stable Idempotency-Key derived from the business event.

   // queue.ts
   import { Queue, Worker } from 'bullmq';
   import IORedis from 'ioredis';
   import { Sndr, SndrError } from '@rkiza/sndr';
   
   const connection = new IORedis(process.env.REDIS_URL!, { maxRetriesPerRequest: null });
   export const emailQueue = new Queue('transactional-email', { connection });
   
   const sndr = new Sndr(process.env.SNDR_API_KEY!);
   
   new Worker(
     'transactional-email',
     async (job) => {
       const { payload, idempotencyKey } = job.data as { payload: Parameters<typeof sndr.emails.send>[0]; idempotencyKey: string };
       return sndr.emails.send(payload, { idempotencyKey });
     },
     {
       connection,
       settings: { backoffStrategy: (attempts) => Math.min(60_000, 1000 * 2 ** attempts) },
     },
   );
   
   // Dispatch from a route:
   await emailQueue.add(
     'order-confirmation',
     {
       payload: { from: 'orders@yourdomain.com', to: customer.email, subject: 'Confirmed', html: '...' },
       idempotencyKey: `order-${orderId}`,
     },
     { attempts: 5 },
   );

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