Trigger WordPress Actions from Email?

You can solve it like this:

1. use wp_schedule_event to check if any user needs to get the mail

2. if yes, send the mail containing a link like

yoursite.com/?user_id=99&myaction=yes&mytoken=sometokenforsecurity

Save that token to the user´s user_meta

    add_user_meta( $user_id, 'mytoken', $token, true )

In your case you obviously need a second link with action=no or whatever you want to call it

3. to catch that link you can use “template_redirect” like this:

   add_action( 'template_redirect', 'my_callback' );
   
   
   function my_callback() {
     // check if variables are sent
     if ( ! $user_id = filter_input( INPUT_GET, 'user_id', FILTER_VALIDATE_INT) )
          return;
     if ( ! $action = filter_input( INPUT_GET, 'myaction' ) )
           return;
     if ( ! $token = filter_input( INPUT_GET, 'mytoken' ) )
           return;
     // check if token is valid
     $saved_token = get_user_meta( $user_id, 'mytoken', true );
     if (!empty($saved_token) && $saved_token == $token) {
           // do the action 
           // delete the token
           delete_user_meta($user_id, 'mytoken');
     }
     // redirect the user to a confirmation page so he knows it worked or did not
     wp_redirect( get_home_url().'/my-confirmation-page');
   
   }
   

Hope that helps!