Migrating from Resend

Sendr's API is intentionally similar to Resend's. Most migrations take under an hour.

Package swap

# Remove Resend SDK
npm remove resend

# Install Sendr SDK
npm install sendr

Initialization

// Before (Resend)
import { Resend } from "resend";
const resend = new Resend(process.env.RESEND_API_KEY);

// After (Sendr)
import { Sendr } from "sendr";
const sendr = new Sendr(process.env.SENDR_API_KEY);

Sending emails

The core send call is nearly identical:

// Before (Resend)
const { data, error } = await resend.emails.send({
  from: "hello@acme.com",
  to: "user@example.com",
  subject: "Hello",
  html: "<p>Hello!</p>",
});

// After (Sendr)
const email = await sendr.emails.send({
  from: "hello@acme.com",
  to: "user@example.com",
  subject: "Hello",
  html: "<p>Hello!</p>",
});

Key differences:

• Sendr throws errors instead of returning { data, error } — wrap in try/catch
• Sendr returns the email object directly (not nested in data)

Error handling

// Before (Resend)
const { data, error } = await resend.emails.send(params);
if (error) {
  console.error(error.name, error.message);
}

// After (Sendr)
import { ApiError, RateLimitError, AuthenticationError } from "sendr";
try {
  const email = await sendr.emails.send(params);
} catch (error) {
  if (error instanceof AuthenticationError) {
    console.error("Bad API key");
  } else if (error instanceof RateLimitError) {
    await sleep(error.retryAfter * 1000);
  } else if (error instanceof ApiError) {
    console.error(error.statusCode, error.code, error.message);
  }
}

REST API endpoint mapping

Feature	Resend	Sendr
Send email	POST /emails	POST /v1/emails
Get email	GET /emails/:id	GET /v1/emails/:id
Update email	PATCH /emails/:id	—
Cancel email	POST /emails/:id/cancel	DELETE /v1/emails/:id
List emails	GET /emails	GET /v1/emails
Send batch	POST /emails/batch	POST /v1/emails/batch
Create domain	POST /domains	POST /v1/domains
List domains	GET /domains	GET /v1/domains
Get domain	GET /domains/:id	GET /v1/domains/:id
Verify domain	POST /domains/:id/verify	POST /v1/domains/:id/verify
Delete domain	DELETE /domains/:id	DELETE /v1/domains/:id
Create API key	POST /api-keys	POST /v1/api-keys
List API keys	GET /api-keys	GET /v1/api-keys
Delete API key	DELETE /api-keys/:id	DELETE /v1/api-keys/:id
Create webhook	—	POST /v1/webhooks
Get webhook	—	GET /v1/webhooks/:id
List webhooks	—	GET /v1/webhooks

All Sendr endpoints are prefixed with /v1/.

Environment variable rename

# .env
# Before
RESEND_API_KEY=re_abc123

# After
SENDR_API_KEY=sndr_live_abc123

React Email compatibility

Sendr is fully compatible with React Email components. No changes needed:

import { render } from "@react-email/render";
import WelcomeEmail from "./emails/welcome";

const html = await render(<WelcomeEmail name="Alice" />);

await sendr.emails.send({
  from: "hello@acme.com",
  to: "alice@example.com",
  subject: "Welcome!",
  html, // React Email rendered HTML works as-is
});

Features available on Sendr but not Resend

• Marketing emails — POST /v1/emails/marketing with automatic List-Unsubscribe headers
• Campaigns — broadcast to contact lists with scheduling and analytics
• Audiences & Contacts — built-in subscriber management
• Test mode — test-mode API keys capture emails to a Test Inbox
• Overage billing — continue sending beyond monthly quota instead of hard cutoff
• Analytics — built-in delivery stats, open/click rates, and benchmarks

Webhook event name differences

Event	Resend	Sendr
Delivered	email.delivered	email.delivered
Bounced	email.bounced	email.bounced
Opened	email.opened	email.opened
Clicked	email.clicked	email.clicked
Complained	email.complained	email.complained

Webhook event names are identical — no changes needed if you're already processing Resend events.

Checklist

• Replace resend package with sendr
• Update import from Resend to Sendr
• Change RESEND_API_KEY to SENDR_API_KEY
• Prefix REST API URLs with /v1/
• Update error handling from { data, error } pattern to try/catch
• Create API keys in Sendr dashboard
• Verify sending domains in Sendr dashboard
• Update webhook endpoints (if any) — event names unchanged