To set or remove the newsletter for a specific user ID, you can use the following API endpoint:
```
xml.php?token=xyz&action=setNewsletterUser&user_id=1&active=1
```
The following applies:
- active = 1: Sets the newsletter for the user.
- active = 0: Deactivates the newsletter for the user.
The API call is returned in the form of true or false, depending on whether the action was successful.