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Resend

Resend is a modern transactional email API. Connecting Resend lets confirmations, reminders, and other customer email appear to come from your verified domain while Hacado sends through your Resend account (no API key paste in the admin UI).

Adding the App​

One-time platform setup (operators)​

Resend has no OAuth-client dashboard. Register a confidential client once per environment with the Register API, then store the returned credentials as secrets. The client_secret is shown only once.

curl -X POST 'https://api.resend.com/oauth/register' \
  -H 'Content-Type: application/json' \
  -d '{
    "client_name": "Hacado",
    "redirect_uris": ["https://<ADMIN_HOST>/apps/oauth/resend/redirect"],
    "grant_types": ["authorization_code", "refresh_token"],
    "response_types": ["code"],
    "token_endpoint_auth_method": "client_secret_basic",
    "scope": "emails:send"
  }'

Set:

  • RESEND_OAUTH_CLIENT_ID
  • RESEND_OAUTH_CLIENT_SECRET

Redirect URI must match {ADMIN_URL}/apps/oauth/resend/redirect. Add extra URIs (up to 10) for local/staging hosts if needed. Do not call register on each org install - Hacado is one remote client; orgs only authorize it.

These OAuth secrets are separate from platform system mail (RESEND_API_KEY / EMAIL_PROVIDER=resend).

In Hacado​

  1. In Resend, verify the domain you will send from (DNS / DKIM as Resend documents).
  2. Open Apps, then Store, and install Resend.
  3. Click Connect, approve access on Resend’s consent screen (emails:send only).
  4. Enter Sender email (must be on a verified domain) and optional Sender name, then save.
  5. Under Default apps, set Resend as the email sender if it is not selected automatically.

Mis-typed From addresses and unverified domains are the usual failure modes. Apps troubleshooting covers retries.

Good to know​

Access tokens expire after about 15 minutes; Hacado refreshes them automatically. Refresh tokens rotate on every use.

Usage​

Branded confirmations from @yourbiz.com​

Use this when: Clients should recognise your domain in the sender field without running your own SMTP server.

You need: A Resend account with that domain verified, and the same address configured as Sender email in the app.

High volume reminders on busy days​

Use this when: You anticipate many appointment updates in one burst.

You need: Sending limits high enough on your Resend plan.

Removing the App​

  1. Open Apps, then Installed apps.
  2. Disconnect Resend.

What changes afterward​

Outbound customer mail falls back to whatever default Hacado uses when no email-sender app is set. You can also revoke access from the Resend dashboard.

Outside Hacado​

Revoke the Hacado OAuth grant in Resend if you no longer use the integration.