Migrate from SparkPost to emailr_

The code change

A typical SparkPost send call next to its emailr_ equivalent.

import SparkPost from 'sparkpost'

const client = new SparkPost(process.env.SPARKPOST_API_KEY)

await client.transmissions.send({
  campaign_id: 'receipts',
  content: {
    from: 'hello@mail.acme.com',
    subject: 'Your receipt',
    html: '<p>Thanks for your order.</p>',
  },
  recipients: [{ address: 'user@example.com' }],
  metadata: { order_id: '123' },
})

import { Emailr } from 'emailr'

const emailr = new Emailr({ apiKey: process.env.EMAILR_API_KEY! })

await emailr.emails.send({
  from: 'hello@mail.acme.com',
  to: 'user@example.com',
  subject: 'Your receipt',
  html: '<p>Thanks for your order.</p>',
  tags: { campaign: 'receipts', order_id: '123' },
})

SparkPost concepts in emailr_

Use this table to find where each feature you rely on lives in emailr_.

How to migrate from SparkPost

1. 01

   Create an API key

   Create a key under API keys in the dashboard. Keys start with et_live_ and are scoped to one domain workspace. Store it as EMAILR_API_KEY in your secret manager or environment, never in client-side code.

2. 02

   Add and verify your sending domain

   In the dashboard, open Domains and add the domain you send from. A subdomain such as mail.yourcompany.com keeps transactional reputation separate from your corporate mailbox.

   Emailr generates the DNS records: a DKIM TXT record on the emailr._domainkey selector, an SPF TXT record, and an MX + TXT pair on the send subdomain used as the MAIL FROM / Return-Path. A DMARC record is optional but recommended.

   SparkPost uses a scph…._domainkey selector and a separate bounce domain CNAME. Keep them until you finish the cutover.

   Emailr's DKIM selector and send subdomain don't collide with other providers' records, so you can add them before cutting over and send from both providers during the migration. A domain can only have one SPF record: if one already exists, merge Emailr's include: into it instead of adding a second record.

3. 03

   Replace transmissions

   Install the SDK. For one-to-one messages, replace transmissions.send() with emails.send(): the content object's from, subject, html and text move to the top level and recipients[].address becomes to. campaign_id and metadata move into tags.

   For transmissions sent to a stored recipient list, import the list as contacts, group them in a segment and send a Broadcast instead.

   Terminalbash

   npm install emailr

4. 04

   Move stored templates

   Recreate templates in emailr_ and pass values in template_data instead of substitution_data.

   Emailr templates substitute flat {{variable}} tokens from template_data. There are no loops or conditionals, so pre-render lists and optional blocks in your code and pass the result as a variable. SparkPost's {{if}} and {{each}} blocks need the same treatment.

5. 05

   Move the suppression list

   Export the SparkPost suppression list and import the addresses as contacts with subscribed: false so broadcasts skip them.

6. 06

   Recreate your event webhooks

   SparkPost batches events into arrays of msys objects. emailr_ sends one event per request with a flat { event, data } body.

   Create a webhook of type transactional (delivery and engagement events), domain (verification status) or receiving (inbound email). Each webhook has its own signing secret. Every request carries an X-Emailr-Signature header: a hex-encoded HMAC-SHA256 of the raw request body. Verify it before trusting the payload.

   verify-webhook.tsts

   import { createHmac, timingSafeEqual } from 'node:crypto'
   
   // rawBody must be the exact request body string, before JSON.parse
   export function isValidEmailrWebhook(rawBody: string, signature: string | null) {
     if (!signature) return false
     const expected = createHmac('sha256', process.env.EMAILR_WEBHOOK_SECRET!)
       .update(rawBody)
       .digest('hex')
     const a = Buffer.from(expected)
     const b = Buffer.from(signature)
     return a.length === b.length && timingSafeEqual(a, b)
   }
   
   // const ok = isValidEmailrWebhook(body, req.headers.get('x-emailr-signature'))
   // const { event, data } = JSON.parse(body)  // e.g. event === 'email.bounced'

Webhook event mapping

emailr_ webhooks post one JSON event per request with an event name and a data object. Translate event names in your handler with this table.

Things to watch for

• Per-recipient substitution_data inside one transmission isn't supported; send per recipient or use Broadcasts with contact properties.
• SparkPost's EU and US hosts are separate; emailr_ uses a single API base URL.
• Remove SparkPost's DNS records only after your last transmission has been sent.

Frequently asked questions

Keep going