Push notifications, attached to an application or website, and controllable by a user on that basis, are the solution for corporate messaging at scale.
This will get you banned. It’s not a question of if, but when. Users will hit the report spam button. Apple will shut you down.
I don’t need more iMessage spam.
what you encourage and what actually happens are two different things, though. gmail does not actively encourage spam, yet most spam emails i receive are from gmail addresses.
you have to actively fight against malicious uses, like spam. "not encouraging" is nowhere near enough.
what systems/processes/safeguards do you have in place to prevent abuse?