Add Captchainbox to Email Security Tools

awesome-privacy.yml

@@ -1090,6 +1090,14 @@ categories:
           Verifies DKIM signatures and shows the result in the e-mail header, in order to help
           spot spoofed emails (which do not come from the domain that they claim to).
 
+      - name: Captchainbox
+        url: https://captchainbox.com
+        description: |
+          CAPTCHA-based email filtering for Gmail. Known contacts get through instantly,
+          while unknown senders receive an auto-reply with a simple CAPTCHA challenge.
+          Verified senders are automatically whitelisted. Helps block spam and unwanted
+          outreach without maintaining complex filter rules.
+
       notableMentions: >
         If you are using ProtonMail, then the [ProtonMail Bridge](https://protonmail.com/bridge/thunderbird)
         enables you to sync & backup your emails to your own desktop mail client.