# Error: Unauthorized: key not found (Brevo)

Source: https://catalystgroup.gg/docs/email-delivery/error-unauthorized-key-not-found/
Updated: 2026-10-19 · By Duane Garner

Brevo cannot find the API key the plugin sent. It was deleted, mistyped, or is an SMTP key rather than a v3 API key.

This article is for sites using the **Brevo** mailer where a send fails with "Key not found".

 

> **The error as you see it:** `Unauthorized: Key not found`
>  
> Shown by the **Brevo** mailer, in the failed-send banner, in **Tools → Debug Events** and in the **Email Log**. Brevo returns it with HTTP status 401.

 

## What this error means

 

The plugin sends each email to Brevo's API with your **API Key**. Brevo looked for that key among the account's API keys and found nothing. Unlike the IP-related "Unauthorized" error, the problem here is the key itself.

 

## Common causes

 
- **An SMTP key was pasted instead of an API key.** Brevo makes two kinds of keys on the same page. SMTP keys start with `xsmtpsib-` and work only for SMTP sign-in. The **Brevo** mailer needs a v3 API key, which starts with `xkeysib-`.
- **The key was deleted** in Brevo.
- **The key was copied incompletely**, or with a leading or trailing space.
- **The key belongs to another Brevo account**, for example a client's account when you meant your own.
- **A `CRMNG_SMTP_*` constant in wp-config.php** still holds an old key.

 

## How to fix

 
1. Open Brevo's keys page
  Sign in to `https://app.brevo.com/`, open the account menu at the top right, and choose **SMTP & API**. Select the **API Keys** tab (not the SMTP tab).
2. Check the existing key
  If the key your site uses is missing from the list, it was deleted. Brevo shows only part of each key after creation, so you cannot copy an old one again.
3. Create a new API key
  Choose **Generate a new API key**, name it after your site, and copy the full key straight away. Check that it starts with `xkeysib-`.
4. Save it in CRM-NG SMTP
  In **CRM-NG SMTP → Settings → General**, with **Brevo** selected, use **Remove API Key**, paste the key into **API Key** and press **Save Settings**.
5. Check for constants
  If the field cannot be edited, the key is set in `wp-config.php` with a `CRMNG_SMTP_*` constant. Update it there.
6. Send a test
  Go to **CRM-NG SMTP → Tools → Email Test**, fill in **Send To** and press **Send Email**.

 

## Verify it worked

 

The test page shows "Test email sent successfully! Check your inbox to confirm delivery." The message also shows in Brevo's transactional email logs.

 

## Notes

 
- If you want to keep an SMTP key, use it only with the **Other SMTP** mailer (host and login are shown on Brevo's SMTP tab). The **Brevo** mailer is the better choice for most sites.
- Delete keys you no longer use, so a leaked old key cannot be misused.
- If the error mentions an IP address or verification instead, see [Unauthorized: not verified or IP not authorized](https://catalystgroup.gg/docs/email-delivery/error-brevo-unauthorized/).

 

## Related

 
- [Brevo (formerly Sendinblue)](https://catalystgroup.gg/docs/email-delivery/mailer-brevo/)
- [Error: Unauthorized: not verified or IP not authorized (Brevo)](https://catalystgroup.gg/docs/email-delivery/error-brevo-unauthorized/)
- [Error: Invalid API key](https://catalystgroup.gg/docs/email-delivery/error-invalid-api-key/)
- [Troubleshooting email delivery](https://catalystgroup.gg/docs/email-delivery/troubleshooting/)