We want to apply a redirection for unsubscriptions for a particular client, so it passes the data to their own ecommerce system. I found how to do this in the documentation (topic 86) using the blah.php?email=[email]settings field. Unfortunately though, the client also uses a custom field for which they put the customers ID on their system. They want to pass this data through the querystring as a secondary check, rather than just having an open unsubscribe link that you could put anyones email address into, which does make sense.
I tried the logical way of doing this, ie just putting in the custom field id so its now:
blah.php?email=[email]&ID=[customerID] (where customerID is the name of the custom field)
Unfortunately though only the [email]is replaced.
Is there any way around this, or is it something that could be added in?