Currently the only way to create automatic shipping tracking emails is through the setup of Mandrill via Mailchimp. This is handled internally by the Support Team.
The only restriction with this setup is you cannot have a separate subscription for Mandrill (essentially you must be a paying customer of Mailchimp to access Mandrill, effectively locking you in a subscription with Mailchimp).
If we were to have the possibility to subscribe to a web-hook event for whenever postage is purchased, and with the webhoook returning essentially the same data as it currently does to Mandrill, it would allow customers who may want a different provider to create their own custom setup.