This is critical functionality for various reasons including managing subscribed lists based on actions taken by a contact and to track affiliate/partner conversions via links. This severely limits transactional email options. The fact that this is not available currently and is apparently not a priority is baffling. It seems CC is focused on simple use cases that do not include API integrations and serious marketing. I'm frustrated that I have spent time developing to an API where maintenance and functionality is not a priority. Other developers beware!   These are additional issues: Unable to GET a list of custom fields via the API Unable CRUD custom fields with names via the API Just recently the options to update custom fields via the API have stopped working Unable to manage tags via the API Unable to use dynamic links When editing lists or contacts, unable to see current tags or lists in UI Receiving this response intermittently when using the API: Service Unavailable: Back-end server is at capacity 503   ... View more