### [Unauthorized: Key Not Found](https://wpmailsmtp.com/docs/unauthorized-key-not-found/)

**Published:** May 17, 2026
**Author:** David Ozokoye

**Content:**

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

## What This Error Means

The API key stored in WP Mail SMTP doesn’t exist in the Brevo account. Brevo looked up the key and returned “unauthorized: Key not found” because no matching key exists on their end.

## Common Causes

- API key was deleted from the Brevo dashboard
- You copied the masked version of an existing key instead of the full key (Brevo masks keys after creation, and the full key cannot be viewed again)
- Typo or extra whitespace when copying the key
- API key belongs to a different Brevo account than the one managing the sending domain

## How to Fix

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

### Step 1: Generate a New API Key in Brevo

Log in to your [Brevo account](https://app.brevo.com) and click your **organization name** in the top-right corner of the page.

![Click organization name in the top-right of the Brevo dashboard](https://wpmailsmtp.com/wp-content/uploads/2026/05/dashboard-click-org-menu.png)Click **Settings** in the dropdown menu.

![Click Settings in the dropdown menu](https://wpmailsmtp.com/wp-content/uploads/2026/05/dashboard-click-settings.png)After that, click **SMTP & API** in the left sidebar.

![SMTP & API option in the Brevo settings sidebar](https://wpmailsmtp.com/wp-content/uploads/2026/05/03-settings-page.png)Then click the **API keys & MCP** tab.

![API keys & MCP tab on the SMTP & API page](https://wpmailsmtp.com/wp-content/uploads/2026/05/04-smtp-api-page.png)Click the **Generate a new API key** button (top-right of the page).

![Generate a new API key button](https://wpmailsmtp.com/wp-content/uploads/2026/05/05-api-keys-tab.png)Enter a name for the key (e.g., “WP Mail SMTP”) and click **Generate**.

![Click Generate in the API key modal](https://wpmailsmtp.com/wp-content/uploads/2026/05/06-generate-modal.png)Copy the API key immediately from the modal. The full key is only shown once. After you close the modal, Brevo masks it, and you can’t retrieve it.

![Copy the API key from the modal](https://wpmailsmtp.com/wp-content/uploads/2026/05/07-copy-api-key.png)### Step 2: Paste the New Key in WP Mail SMTP

Go to **WP Mail SMTP » Settings** and click the **General** tab, scroll to the Brevo section, and clear the **API Key** field.

![Brevo API Key field in WP Mail SMTP](https://wpmailsmtp.com/wp-content/uploads/2021/02/Sendinblue-api-key.png)Then paste the new API key and click **Save Settings**.

### Step 3: Send a Test Email

Go to **WP Mail SMTP » Tools**. Click the **Email Test** tab.

![Email Test tab in WP Mail SMTP Tools](https://wpmailsmtp.com/wp-content/uploads/2021/09/Email-test-tab-in-WP-Mail-SMTP.png)Enter a recipient email in the **Send To** field. Leave the **HTML** toggle ON.

Once done, click **Send Email**.

![Send Email button in the Email Test tab](https://wpmailsmtp.com/wp-content/uploads/2022/08/wp-mail-smtp-send-test-email-1.png)Look for the success message, then check your inbox to confirm the email arrived.

## Notes

- Brevo masks API keys after creation. If you see a partially hidden key on the API keys page, do not copy it. Generate a new one instead.
- The full API key starts with `xkeysib-`. Make sure the value you paste includes the complete string with no extra spaces.
- If the error persists after replacing the key, confirm you are logged into the same Brevo account that owns the sending domain configured in WP Mail SMTP.

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

**Categories:** Brevo Errors, Error Library

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