# Resend

Source: https://catalystgroup.gg/docs/email-delivery/mailer-resend/
Updated: 2026-10-19 · By Duane Garner

Connect CRM-NG SMTP to Resend with an API key that has sending access and a verified domain.

This guide shows you how to send your WordPress email through Resend, a modern email API popular with developers. It suits sites that want quick setup and a tidy dashboard. Resend has a free plan with monthly and daily limits; check its site for the current figures.

 

The **Resend** mailer sends through Resend's API with an API key. Resend only delivers mail from domains you have verified.

 

## Before you start

 
- A Resend account (sign up at `https://resend.com/`).
- A domain you control, with access to its DNS records.
- Administrator access to your WordPress site.

 

## Step 1: Add and verify your domain

 
1. Sign in to Resend
  Go to `https://resend.com/` and sign in.
2. Open Domains
  Open **Domains** in the side menu and choose **Add Domain**.
3. Enter the domain
  Type the domain you send from and pick a region close to your audience if Resend asks.
4. Publish the records
  Resend lists a DKIM TXT record, plus an MX and an SPF TXT record on a sending subdomain (usually `send.yourdomain.com`). Add them at your DNS provider exactly as shown.
5. Verify
  Return to Resend and press **Verify DNS Records** until the domain shows as verified.

 

> **Before your domain is verified:** Without a verified domain, Resend only lets you send test messages from its shared testing address to your own account email. Your website's normal mail will be refused until the domain is verified.

 

See [Adding DNS records](https://catalystgroup.gg/docs/email-delivery/dns-records/) for help with DNS.

 

## Step 2: Create an API key

 
1. Open API Keys
  Open **API Keys** in the side menu (the plugin's link goes to `https://resend.com/api-keys`) and choose **Create API Key**.
2. Name it
  Use a name that identifies the site.
3. Set the permission
  Choose **Sending access**. You can also limit the key to your verified domain.
4. Copy the key
  Create the key and copy it now; it starts with `re_` and Resend shows it once.

 

## Step 3: Connect in CRM-NG SMTP

 
1. Choose the mailer
  In WordPress, open **CRM-NG SMTP → Settings → General** and set **Mailer** to **Resend**.
2. Paste the key
  Paste the key into **API Key**.
3. Set the sender
  Set **From Email** to an address on your verified domain, for example `hello@yourdomain.com`, and set **From Name**. Tick **Force From Email** so other plugins cannot use an unverified domain.
4. Save
  Press **Save Settings**.

 

## Send a test email

 

Open **CRM-NG SMTP → Tools → Email Test**, enter your address in **Send To**, and press **Send Email**. Resend's **Emails** page shows the message and its delivery events. See [Sending a test email](https://catalystgroup.gg/docs/email-delivery/send-a-test-email/).

 

> **About the SPF warning:** The test page checks the SPF record of your main domain and expects it to include `amazonses.com`. Resend places its SPF record on the sending subdomain instead, so this check may warn even when Resend shows everything as verified. Trust the verified status in Resend and check that DKIM and DMARC pass in a received message.

 

## Troubleshooting

 
- The key is wrong, deleted, or limited to another domain: [401 Unauthorized or Forbidden](https://catalystgroup.gg/docs/email-delivery/error-401-unauthorized-or-forbidden/) and [Invalid API key](https://catalystgroup.gg/docs/email-delivery/error-invalid-api-key/)
- The From domain is not verified: [553 Sender address rejected](https://catalystgroup.gg/docs/email-delivery/error-553-sender-address-rejected/)
- You hit the daily or monthly limit, or sent too fast: [Email sending limit reached](https://catalystgroup.gg/docs/email-delivery/error-email-sending-limit/)
- The recipient bounced or complained before: [Email address in suppression list](https://catalystgroup.gg/docs/email-delivery/error-email-in-suppression-list/)
- Mail arrives in spam: [Emails landing in spam](https://catalystgroup.gg/docs/email-delivery/emails-landing-in-spam/)

 

## Related

 
- [Choosing a mail service](https://catalystgroup.gg/docs/email-delivery/choose-a-mailer/)
- [Adding DNS records: SPF, DKIM and DMARC](https://catalystgroup.gg/docs/email-delivery/dns-records/)
- [Verifying your DNS records](https://catalystgroup.gg/docs/email-delivery/verify-dns-records/)
- [Sender name, address and the Force settings](https://catalystgroup.gg/docs/email-delivery/sender-name-and-address/)
- [Debug events](https://catalystgroup.gg/docs/email-delivery/debug-events/)