[Email Security] Add API link (#16777)

* [Email Security] Add API link

* Correct API link

Author: Maddy-Cloudflare

src/content/docs/cloudflare-one/insights/email-monitoring/search-email.mdx

@@ -122,7 +122,7 @@ With Email Security, you can export messages to a CSV file.
 To export messages:
 
 1. On the **Investigation** page, under **Your matching messages**, select **Export to CSV**.
-2. Select **Export messages** on the pop-up message. You can only export up to 1,000 rows from the dashboard.
+2. Select **Export messages** on the pop-up message. You can only export up to 1,000 rows from the dashboard. To export all matching messages, use the [API](/api/operations/email_security_get_message).
 
 ## Email status