feat: first pass at 1-click unsubscribe docs

Author: connorlindsey

content/preferences/commercial-unsubscribe.mdx

@@ -1,8 +1,69 @@
 ---
-title: "Commercial unsubscribe"
-description: "Learn how to enable 1-click unsubscribe links for commercial notifications."
-tags: ["recipients", "unsubscribe", "commercial", "prefs", "preferences"]
+title: "Commercial Unsubscribe"
+description: "Learn how to manage commercial email unsubscribe functionality in Knock"
+tags: ["preferences", "unsubscribe", "commercial", "broadcasts", "workflows"]
 section: Preferences
 ---
 
-To comply with CAN-SPAM, you can mark a workflow or broadcast as commercial if it sends commercial or promotional messages. You can include a 1-click unsubscribe link in your templates and Knock will handle sending the appropriate email headers.
+Knock provides built-in support for commercial email unsubscribe functionality, allowing recipients to opt out of promotional or commercial messages with a single click.
+
+## How commercial unsubscribe works
+
+When you mark a workflow or broadcast as commercial, Knock automatically handles the necessary unsubscribe functionality:
+
+1. Adds required unsubscribe headers to all emails sent through that workflow or broadcast
+1. Provides an unsubscribe URL variable that can be included in your email templates
+1. Manages recipient opt-outs during preference set evaluation
+
+## Configuring commercial workflows
+
+To enable commercial unsubscribe functionality for a workflow or broadcast:
+
+1. Navigate to the workflow or broadcast
+1. For a workflow, click "Manage workflow". For a broadcast, click "Edit details".
+1. Toggle "Commercial"
+1. Save your changes
+
+Once enabled, Knock will automatically include the necessary unsubscribe headers in all emails sent through that workflow.
+
+## Adding unsubscribe links to emails
+
+### Using footer links
+
+When configuring an email layout using the visual editor, you can toggle the "Include commercial unsubscribe link" input to include the unsubscribe link.
+
+### Using the code editor
+
+You can add an unsubscribe link to your email layouts or templates using the built-in variable:
+
+```liquid title="Show unsubscribe link"
+<a href="{{vars.commercial_unsubscribe_url}}">Unsubscribe</a>
+```
+
+You can conditionally include the link by checking if the variable is present:
+
+```liquid title="Show unsubscribe link only for commercial messages"
+{% if vars.commercial_unsubscribe_url %}
+<a href="{{vars.commercial_unsubscribe_url}}">Unsubscribe</a>
+{% endif %}
+```
+
+## Configuring the confirmation page
+
+When a user unsubscribes by directly clicking the unsubscribe link in a message, Knock will display a confirmation page indicating they have been succesfully unsubscribed from commercial messages. You can customize this page by navigating to "Developers" > "Preferences", then clicking the "Unsubscribe" tab.
+
+### Standard confirmation page
+
+You can customize the title and body text that will appear on the Knock confirmation page.
+
+### Custom redirect URL
+
+You can provide a URL that recipient's should be redirected to after unsubscribing.
+
+## Preference evaluation rules
+
+When a recipient clicks the unsubscribe link, their default preference set will be updated, marking `commercial_unsubscribe` as true. They will be opted-out of commercial messages, and they will continue to receive transactional messages based on their other preferences.
+
+## Learn more
+
+To learn more about managing recipient preferences and building preference centers with Knock, visit our [preferences overview](/preferences/overview).