How to include a link / response in email to update a field in record?

Hi there,

My app "Booking Management" sends an email notification to "freelance clerks" with appointment details.
They need to accept or decline this appointment.

Email notification set up under deluge script - no problem.
Custom action "accept" & "decline" in Zoho Creator report - no problem

Now there is my problem - I would like to include the option to "accept" or "decline" in the email & update the record.

I have set up a stateless form (link to main form create a booking) to embed in the email:
- however it does not embed properly in the email: only the buttons show
- when clicking of these buttons, nothing happens.

I have included a link in the email to open the stateless form, however the "freelance clerks" would have to browse through all the appointments (through drop down list) to find their appointment. But then the record is updated accordingly.

Any advice? Going through PostURL or XML (which I don't understand)
The idea is similar to the options of subscribing / unsubscribing often found at bottom of emails,

Thanks in advance for your ideas and advices,

Kind regards,
Claire