sorry for not getting back to you earlier.
Unfortunately, this is not something I plan to implement in the future. Unlike other apps, Deliveries fetches all shipment information directly from the servers of the actual couriers without routing everything through my own system. So your device does all the actual work itself.
In order to send emails on each update, all your tracking information would need to be stored on my server and I'd need to have a system that continuously checks for updates on the courier websites (i.e. for every active delivery of every app user, which is multiple millions).
Thanks for your understanding!