Hi Jens.
Thanks for your detailed question and for putting our plugins through the ringer. I hope they turn out to be worth the effort for you! I’ll do my best to help.
As a starting point, I’d suggest searching for “do_action” throughout this file: /wp-content/plugins/event-tickets-plus/src/Tribe/Commerce/WooCommerce/Main.php
You’ll see actions in there for things like:
- ticket created or ticket generated
- ticket check-in
- complete ticket order
You could leverage one of those action hooks to generate a new email, either using wp_mail() or the WC_Email class.
I cannot advise on how/if to use Follow Ups, but I’d guess it could tie in to Event Tickets’ / Event Tickets Plus’ hooks.
If you need some coding help, you may want to ask your developer or reference our list of known customizers.
I hope this information helps!