# Mailgun

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

Connect CRM-NG SMTP to Mailgun with an API key, your verified sending domain and the matching US or EU region.

This guide shows you how to send your WordPress email through Mailgun, a developer-friendly transactional email service. It suits sites that want detailed logs and control, and businesses that need to keep data in the EU. Mailgun usually offers a free trial or a small free allowance; check its site for the current terms.

 

The **Mailgun** mailer sends through Mailgun's API. It needs three things that must agree with each other: an API key, the sending domain, and the region (US or EU) where that domain lives.

 

## Before you start

 
- A Mailgun account (sign up at `https://www.mailgun.com/`). Mailgun sends an activation email when you sign up; click the link in it before you go on.
- A domain you control, with access to its DNS records. Mailgun suggests a subdomain such as `mg.yourdomain.com`.
- Administrator access to your WordPress site.

 

## Step 1: Add and verify your sending domain

 
1. Sign in to Mailgun
  Go to `https://app.mailgun.com/` and sign in.
2. Open the domains list
  Open **Send → Sending → Domains** (the plugin's **Get a Domain Name** link goes there).
3. Add a domain
  Choose **Add new domain** and enter it, for example `mg.yourdomain.com`.
4. Pick the region
  Choose **US** or **EU**. You cannot move a domain between regions later, so pick EU if you operate under EU data rules.
5. Publish the records
  Mailgun lists TXT records for SPF and DKIM, plus optional MX and CNAME (tracking) records. Add them at your DNS provider.
6. Verify
  Press **Verify DNS settings** in Mailgun until the domain shows as verified.

 

> **The sandbox domain:** Every new account gets a sandbox domain (it starts with `sandbox`). It only sends to recipients you add as authorised, so use it for a quick trial at most. Use your own domain for the live site.

 

## Step 2: Create an API key

 
1. Open API security
  Open the account menu (top right) and choose **API Security** (the direct address is `https://app.mailgun.com/settings/api_security`).
2. Add a key
  In the **Mailgun API Keys** section, choose **Add new key**, give it a description such as your site name, and create it.
3. Copy it
  Copy the key now; Mailgun shows the full key once.

 

## Step 3: Connect in CRM-NG SMTP

 
1. Choose the mailer
  In WordPress, open **CRM-NG SMTP → Settings → General** and set **Mailer** to **Mailgun**.
2. Paste the key
  Paste the key into **Mailgun API Key**.
3. Enter the domain
  In **Domain Name**, type the sending domain exactly as Mailgun lists it, for example `mg.yourdomain.com`. Do not add `https://` or a trailing slash.
4. Pick the region
  Under **Region**, choose **US** or **EU** to match the region you picked for the domain.
5. Set the sender
  Set **From Email** to an address on that domain (or its parent domain) and set **From Name**. Tick **Force From Email** if other plugins change the sender.
6. Set Return Path
  Tick **Return Path** so bounce messages go back to your From Email instead of being lost.
7. 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**. In Mailgun, **Send → Reporting → Logs** (or the logs page for your domain) shows the result. See [Sending a test email](https://catalystgroup.gg/docs/email-delivery/send-a-test-email/).

 

The domain check on the test page looks for `mailgun.org` in the SPF record of the domain in **Domain Name**. See [Adding DNS records](https://catalystgroup.gg/docs/email-delivery/dns-records/).

 

## Troubleshooting

 
- Wrong key, a disabled key, or an account not yet activated: [401 Unauthorized or Forbidden](https://catalystgroup.gg/docs/email-delivery/error-401-unauthorized-or-forbidden/)
- The domain name or region does not match your account: [404 Not Found](https://catalystgroup.gg/docs/email-delivery/error-404-not-found/)
- The key was mistyped: [Invalid API key](https://catalystgroup.gg/docs/email-delivery/error-invalid-api-key/)
- Mailgun disabled the account: [Account blocked](https://catalystgroup.gg/docs/email-delivery/error-account-blocked/)
- You have reached your plan or sandbox limit: [Email sending limit reached](https://catalystgroup.gg/docs/email-delivery/error-email-sending-limit/)
- The recipient bounced before and is blocked: [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/)

 

A 404 almost always means one of three things: the domain is typed differently from Mailgun's list, the region is wrong, or the domain belongs to another Mailgun account.

 

## 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/)
- [Delivery and bounce webhooks](https://catalystgroup.gg/docs/email-delivery/delivery-webhooks/)
- [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/)