### [Error: 404 Not Found](https://wpmailsmtp.com/docs/mailgun-404-not-found/)

**Published:** June 1, 2026
**Author:** David Ozokoye

**Content:**

**Note**: This guide applies to the [Mailgun mailer](https://wpmailsmtp.com/docs/how-to-set-up-the-mailgun-mailer-in-wp-mail-smtp/ "Mailgun") in WP Mail SMTP.

## What This Error Means

Mailgun can’t find the sending domain. The domain name in WP Mail SMTP doesn’t match any domain in the Mailgun account, or it exists in a different region.

## Common Causes

- You entered the domain name incorrectly in WP Mail SMTP (e.g. `yourdomain.com` instead of `mg.yourdomain.com`)
- Domain is in the EU region but WP Mail SMTP region is set to US (or vice versa)
- You deleted the domain from Mailgun
- You used a Mailgun sandbox domain but deleted it or didn’t copy it exactly

## How to Fix

Here is the complete step-by-step guide to resolving the error.

### Step 1: Verify the Domain Name and Region

Start by logging in to [Mailgun](https://app.mailgun.com "Mailgun"). Then, in the left sidebar, click **Sending** and select **Domains**.

![Click Sending then Domains in the sidebar](https://wpmailsmtp.com/wp-content/uploads/2026/05/sending-domains-nav.png)Next, note the exact domain name shown in the domains table (e.g., `mg.yourdomain.com`).

![Domains list page in Mailgun](https://wpmailsmtp.com/wp-content/uploads/2026/05/domains-list-1.png)After that, note the **region** (US or EU) shown in the top navigation bar.

![Region selector in the top navigation bar](https://wpmailsmtp.com/wp-content/uploads/2026/05/region-selector.png)### Step 2: Update WP Mail SMTP to Match

Start by going to **WP Mail SMTP » Settings** and scrolling to the **Mailgun** section.

![WP Mail SMTP settings page](https://wpmailsmtp.com/wp-content/uploads/2023/08/wp-mail-smtp-settings.png)Then, set **Domain Name** to the exact domain name from Step 1.

![Domain Name field in WP Mail SMTP](https://wpmailsmtp.com/wp-content/uploads/2026/05/wp-mail-smtp-domain-name-field.png)Next, set **Region** to match the domain’s region (US or EU).

![Region option in WP Mail SMTP Mailgun settings](https://wpmailsmtp.com/wp-content/uploads/2022/12/mailgun-select-region.png)Finally, click **Save Settings**.

### Step 3: Send a Test Email

To test the fix, go to **WP Mail SMTP » Tools**, click the **Email Test** tab, enter a recipient email in the **Send To** field, leave the **HTML** toggle ON, and click **Send Email**.

![Test email tab](https://wpmailsmtp.com/wp-content/uploads/2024/10/test-email-tab-1024x1002.png)Finally, look for the success message and check your inbox to confirm the email arrived.

## Notes

- Mailgun typically uses a subdomain for sending (e.g. `mg.yourdomain.com` or `mail.yourdomain.com`), not the root domain. The subdomain must match exactly what’s in Mailgun.
- If using Mailgun’s sandbox domain for testing, copy it exactly from the Mailgun dashboard including the `.mailgun.org` suffix.

That’s It! You now know how to fix the ‘404 Not Found’ error in Mailgun and get your emails sending again through WP Mail SMTP.

**Categories:** Mailgun Errors, Error Library

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