# 401 Unauthorized Error

If you're getting an "Unauthorised" error (401 code) when trying to send emails, there are several possible causes and solutions.

### Common Causes

**1. Sending from Unverified Domain**

Make sure you're sending from the domain that you've set up and verified in Mailtrap. Using any other domain will result in this error.

{% hint style="danger" %}
If you verified `example.com`, you can only send from `*@example.com` addresses. Attempting to send from `otherdomain.com` will fail with a 401 error.
{% endhint %}

**2. API Token Permissions**

If you've configured a custom API token for your domain, make sure it has proper permissions to send emails.

Check your [API tokens](https://mailtrap.io/settings/api-tokens) and verify the token has:

* Email sending permissions
* Access to the correct domain
* Valid expiration date (if applicable)

**3. Incorrect Credentials**

Make sure you're using the correct SMTP/API credentials provided in the Integration tab of your domain.

<div data-with-frame="true"><figure><img src="/files/aUP8i3TjC96eXNfiMYfV" alt="Integration tab showing SMTP and API credentials for both Transactional Stream and Bulk Stream in Mailtrap"><figcaption><p>SMTP and API credentials in Integration tab</p></figcaption></figure></div>

### How to Fix

{% stepper %}
{% step %}
**Verify Your Domain**

1. Go to [Sending Domains](https://mailtrap.io/domains)
2. Ensure your domain shows the **Verified** badge
3. If not verified, complete the DNS record setup
   {% endstep %}

{% step %}
**Check API Token (if using custom tokens)**

1. Go to [API Tokens](https://mailtrap.io/settings/api-tokens)
2. Verify the token has **Send Email** permissions
3. Ensure it's assigned to the correct domain
4. Check that the token hasn't expired
   {% endstep %}

{% step %}
**Verify Credentials**

Navigate to: **Sending Domains > Integration > Integrate** (under Transactional or Bulk Stream)

Copy the exact credentials shown there:

* For SMTP: Username and Password
* For API: API Token

Replace your current credentials with these values.
{% endstep %}

{% step %}
**Test with cURL**

Use the cURL code example to test if the error persists:

1. Go to **Sending Domains > Integration > Integrate**
2. Select your stream (Transactional or Bulk)
3. Go to **Code Samples > cURL**
4. Copy and run the cURL command

<div align="left" data-with-frame="true"><figure><img src="/files/TWnjxpzEVEVIFXKqnQoW" alt="Code Samples section in Mailtrap showing cURL integration example" width="563"><figcaption><p>Code Samples section with cURL example</p></figcaption></figure></div>

If the cURL test succeeds but your application fails, the issue is with your application's configuration.
{% endstep %}
{% endstepper %}

### Still Having Issues?

If you've verified all the above and still getting 401 errors:

* Double-check that your FROM address domain matches your verified domain
* Ensure there are no extra spaces or special characters in your credentials
* Contact support at <support@mailtrap.io> with:
  * Your domain name
  * The exact error message
  * A code sample showing how you're attempting to send

### Related Articles

* [Sending Domain Setup](/email-api-smtp/setup/sending-domain.md)
* [API Integration](/email-api-smtp/setup/api-integration.md)
* [SMTP Integration](/email-api-smtp/setup/smtp-integration.md)
* [Sending from Domain Not Allowed](/email-api-smtp/help/troubleshooting/sending-from-domain-not-allowed.md)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.mailtrap.io/email-api-smtp/help/troubleshooting/unauthorized-401-error.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.