Sending notifications is fairly easy to do. Sending an email with a button that you can click to trigger an action is a bit more involved. As you said, you can generate a unique GUID and attach that to the email. This requires some bookkeeping of the GUID. It’s doable, but I would rather not want to make this a standard feature as I am not sure how many users would like this feature. You are certainly welcome to modify the firmware source code yourself to add such features.