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How to set up the Resend integration in Base44

Connect Resend to a Base44 app: verify a sending subdomain, add the API key, build email flows with the AI, and avoid the MX record problem on Base44-bought domains.

7 min read

To use Resend with Base44, verify a sending domain in Resend, create an API key, add Resend from Base44’s integrations catalog and paste the key, then describe your email flows in the AI chat. It needs the Builder plan, because Resend calls run in backend functions. Use a subdomain like send.yourdomain.com for sending.

Not sure you need Resend? Base44’s built-in SendEmail covers most transactional email. The Base44 email guide compares the two.

When Resend is worth it

  • You send more email than your integration credits comfortably cover.
  • You need templates, attachments, audiences or unsubscribe handling.
  • You want deliverability data in Resend’s dashboard.
  • You want to email people who haven’t signed up to your app from a domain you’ve verified in Resend, outside SendEmail’s recipient rules.

Emails sent through Resend go through your own Resend account, so they don’t use Base44’s integration credits. Base44 notes that it doesn’t support issues on Resend’s side.

Part 1: Resend

  1. Sign up at Resend and add your domain. Use a subdomain such as send.yourdomain.com or mail.yourdomain.com.
  2. Add the DNS records Resend gives you (TXT and MX) at your DNS provider.
  3. Wait for Resend to show the domain as verified.
  4. Create an API key on the API Keys page and keep it somewhere safe.

Part 2: Base44

From Base44’s Resend guide, for a new app:

  1. Open the integrations catalog while logged in.
  2. Find Resend and click Use this integration.
  3. Paste your API key when prompted.
  4. Describe what you want in the AI chat, for example Build me an app that sends a welcome email when someone signs up.

For an existing app, ask in the chat:

Add the Resend integration to my app. Prompt me for the API key, and send a welcome
email from hello@send.yourdomain.com when someone subscribes.

The AI stores the key as a secret and generates the backend functions that call Resend.

Common Resend flows on Base44

  • Welcome emails on signup.
  • Password resets and account recovery.
  • Order confirmations and status updates.
  • Internal alerts when forms are submitted.
  • Reminders for incomplete actions.
  • Newsletters to subscribers, with Resend Audiences handling contacts and unsubscribes.

Pair any of them with an automation (Builder plan) to send on a schedule or when data changes.

Check that it works

  1. Trigger the flow on your published app.
  2. Look in Resend’s Emails log for the message and its status.
  3. If it’s missing, check your Base44 app logs for the backend function’s error, then confirm the secret holds the current key.

What to do next

  1. Verify a sending subdomain in Resend.
  2. Add the integration and build one flow end to end.
  3. Add a DMARC record for the sending domain if Resend’s checks suggest it.

Found something wrong or out of date? Base44 ships changes every week and we'd rather fix a guide than let it rot.

Frequently asked questions

Which Base44 plan do I need for Resend?
The Builder plan or higher, because the Resend integration runs through backend functions. On the Free or Starter plans, use Base44's built-in SendEmail instead.
Is Resend free to use with Base44?
Resend has a free tier. Base44's docs describe it as allowing emails from a verified domain, up to 3,000 emails a month and 1,000 marketing contacts. Check Resend's pricing page for current limits. Emails sent through Resend don't use Base44 integration credits.
Should I use a subdomain for Resend?
Yes. Resend requires its MX record on a subdomain host such as send.yourdomain.com, and a subdomain like mail.yourdomain.com keeps your sending reputation separate from your main domain.
What if I bought my domain through Base44?
Base44's docs say MX records on Base44-bought domains are set by the email provider you connect and can't be edited by hand, so contact Base44 support with the host, value and priority Resend gives you.

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