Emailing Churned Users with Feedback Form?

[cormacncheese]

Apologies if this is a duplicate post but I was unable to find an answer for it on the forums or in the docs.

In the past when I've deleted apps, I've received an email from the app owner asking for feedback on why I uninstalled the app.

My question is, is this allowed? If so can I do so manually or do I need to use webhooks?