My tasks are created from customer requests. So, I'd like the customer to be able to email Trello and receive notifications when the card reaches the final list.
This is easy if the customer is a member of the board, but I don't want customers to see each others incoming requests, nor our internal processes, and they are in any case not interested in signing up for this Trello board.
What is the best way to do get this sort of interaction? Perhaps some sort of integration with Zendesk (which we have licenses to)?