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Connect Resend to RadarSend

Resend is an email sending service. This guide walks you through connecting it to RadarSend so you can send email and track delivery, bounces, and complaints.

Before you begin#

  • A Resend account — sign up at https://resend.com if you don’t have one.
  • Access to your domain’s DNS settings (so you can add the records Resend gives you).
  • A RadarSend account with admin access.

Step 1 — Get your Resend credentials#

  1. Sign in to Resend.
  2. Add and verify your sending domain. Go to Domains→Add Domain, enter your domain, and Resend will show you a set of DNS records (DKIM, SPF, and a return-path/MX record). Add each record with your DNS provider, then click Verify DNS Records. Verification can take a few minutes to a few hours while DNS propagates. Your domain shows as Verified once it’s ready.
  3. Create an API key. Go to API Keys→Create API Key, give it a name, and choose the Full access permission. Click to create it, then copy the key — it starts with re_ and is shown only once, so save it somewhere safe.
    • Resend offers only two permissions, Full access and Sending access, with nothing in between. RadarSend needs more than sending: the connection test reads your domains, and webhook setup creates a webhook. A Sending access key can send, but it fails both of those, so use Full access.

Step 2 — Add the sending service in RadarSend#

  1. In RadarSend, go to Settings→Sending→Sending services and click + Connect a service.
  2. In the wizard, on Choose your sending service, pick Resend, then click Continue.
  3. On Enter your Resend keys, paste your API Key. Leave Webhook signing secret empty; RadarSend fills it in during Step 3. Then click Connect & verify.

RadarSend saves the service and runs a live connection test against Resend. When the key works, it shows Connected · Resend · {N} domains.

Step 3 — Delivery, bounce & complaint tracking#

RadarSend sets this up for you as part of Connect & verify. Once the connection test passes, the wizard shows Setting up event webhooks…, then Event webhooks configured. It creates a Resend webhook that points at your RadarSend account with these events:

email.delivered
email.bounced
email.complained

It also saves the webhook’s Signing Secret for you, so RadarSend verifies every event Resend sends without you copying anything.

To check it later, open the service at Settings → Sending → Sending services → your service. The Webhook delivery section shows Configured with the Bounce, Spam Complaint, and Delivery triggers. Click Re-check to run the check again. Configure webhooks (or Re-configure webhooks) only appears when something needs fixing; fix the cause, then click it to retry.

Step 4 — Confirm your sending address#

  1. Go to Settings→Sending→Senders and click + Add sender.
  2. Enter your Sending address (it must be on your verified Resend domain) and click Continue. Add a Display name and Reply-to, pick the email types this sender handles, then click Continue.
  3. On Tracking & confirm, choose this service under Sending service (only shown if you have more than one), enter a test recipient, and click Send test.
  4. When the test is accepted, click Save sender.

If Resend rejects the test, RadarSend shows Resend didn’t accept this address with Resend’s reason and, when your key can read it, what Resend currently says about the domain (for example Pending) or that the domain isn’t on the account yet. Verify the domain in Resend using the Open Domains in Resend link, then retry. RadarSend doesn’t add domains to your Resend account; that’s always done in Resend.

Tip: open the service to see the Verified sending domains section, which lists the domains on your Resend account and their status. It loads when you open the page; Re-check refreshes it.

Common issues#

  • “The signing secret saved in RadarSend doesn’t match…” or “RadarSend isn’t checking signatures…” under Webhook delivery. The secret RadarSend has saved isn’t the one on its webhook in Resend (for example, after connecting keys from a different Resend account). Click Re-configure webhooks and RadarSend fetches the current secret. Until then, a mismatched secret means events are rejected.
  • Domain not verified / DNS not propagated. If sending fails, check Domains in Resend — the domain must show Verified. DNS changes can take minutes to hours to propagate; if records don’t validate, re-check them against what Resend shows and click Verify DNS Records again.
  • From-address isn’t on a verified domain. Your sending address must use a domain you’ve verified in Resend. An address on an unverified (or slightly misspelled) domain will be rejected.
  • Free plan / testing restrictions. Until you’ve verified a domain, Resend limits you to sending test emails to your own account’s email address (using its sandbox address). Verify your domain to send to real recipients.
  • “Invalid API key” when you connect. The key has Sending access. It can send, but it can’t read your domains or create a webhook, so the connection test fails and webhooks aren’t set up. Create a Full access key and update it under API credentials, then click Configure webhooks.

Good to know#

  • Resend signs its webhooks (using Svix under the hood). RadarSend stores the signing secret when it creates the webhook and uses it to verify that each event came from Resend. If you ever recreate the webhook in Resend yourself, paste its new secret into Webhook signing secret.