The SNDR alternative to Mailchimp Transactional.

Mailchimp Transactional, formerly Mandrill, is an add-on to a paid Mailchimp plan and fits teams that already work in Mailchimp. SNDR is standalone: a free plan, idempotency keys and webhooks signed with HMAC-SHA256 over the body. Mailchimp Transactional is ahead on integration with Mailchimp audiences and templates.

1. 1

   Install the SDK

   Add @rkiza/sndr alongside @mailchimp/mailchimp_transactional. They coexist while you cut over.

   pnpm add @rkiza/sndr

2. 2

   Replace the send call

   Mandrill’s messages.send maps to sndr.emails.send. message fields become flat top-level fields.

   // before
   import mandrill from '@mailchimp/mailchimp_transactional';
   const mc = mandrill(process.env.MANDRILL_API_KEY!);
   await mc.messages.send({
     message: {
       from_email: 'me@yourdomain.com',
       to: [{ email: 'a@b.com', type: 'to' }],
       subject: 'hi',
       html: '<p>hi</p>',
     },
   });
   
   // after
   import { Sndr } from '@rkiza/sndr';
   const sndr = new Sndr(process.env.SNDR_API_KEY!);
   await sndr.emails.send({
     from: 'me@yourdomain.com', to: 'a@b.com', subject: 'hi', html: '<p>hi</p>',
   });

3. 3

   Migrate templates

   Mandrill templates use Mailchimp merge tags (*|NAME|*) or Handlebars. SNDR templates use {{ name }} placeholders, so replace merge tags when you recreate a template; Handlebars helpers may need a small refactor.

4. 4

   Migrate webhook handlers

   Mandrill posts form-encoded with a SHA-1-HMAC of URL + sorted params. SNDR posts JSON with a timestamp-prefixed HMAC-SHA256. Use the shipped verifier.

   import { verifyWebhookSignature } from '@rkiza/sndr';
   
   app.post('/webhooks/sndr', express.raw({ type: 'application/json' }), (req, res) => {
     if (!verifyWebhookSignature(req.body, req.header('x-sndr-signature') ?? '', process.env.SNDR_WEBHOOK_SECRET!)) {
       return res.status(400).send('bad signature');
     }
     res.status(200).send('ok');
   });

5. 5

   Reuse your DNS

   SPF can keep both includes during cutover. Add a fresh DKIM record (selector + value generated by SNDR when you add the domain).