> ## Documentation Index
> Fetch the complete documentation index at: https://jetemail.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# 550 [ACL]

> Email rejected due to unauthorized sending domain

### Introduction

This error occurs when attempting to send email from a domain that is not authorized for your SMTP user account.

### Example Error Message

Here's what this error looks like:

```
user@example.com
   host relay.jetsmtp.net [103.173.0.0]
   SMTP error from remote mail server after end of data:
   550 [ACL] Blocked. See https://reports.jetsmtp.net/?id=000000000000000000&auth=smtpuser
```

### What Does This Mean?

Our access control system has blocked your email because:

* The sending domain is not authorized for your account
* Your SMTP credentials don't have permission to send from this domain
* Domain authentication hasn't been properly configured

### How to Fix This Error

<Note>
  **Check the SMTP user's permission mode first.** The most common cause of this block is the SMTP user not being allowed to send from the `From` domain. Open **Outbound** → **SMTP** → your SMTP user and check the permission mode:

  * **Default:** only domains explicitly assigned to this user. Add the sender domain to the user's allowed list.
  * **Allow all domains:** any domain on your account. If your sender domain isn't in **Outbound** → **Domains** yet, add it there.
  * **Allow any domain** (Pro): any domain at all. If you're on Pro and expect this, make sure the toggle is actually on.

  See [SMTP users → permission modes](/outbound/smtp-users#permission-modes) for the full breakdown.
</Note>

1. Verify the "From" address matches a domain the SMTP user is allowed to send from (see note above)
2. Check the SMTP user's [permission mode](/outbound/smtp-users#permission-modes) and adjust if needed
3. If the domain should exist on your account, add and verify it under **Outbound** → **Domains**
4. Ensure proper SPF and DKIM records are configured for the sending domain

### Prevention

To avoid this error in the future:

* Only send from domains that are authorized for your account
* Keep an updated list of your approved sending domains
* Request domain authorization before attempting to send
* Regularly review your account's domain settings