Thus we built Balto - an API to send iMessages, and were able to transition our entire customer list successfully (as well as take advantage of iMessage features like unlimited messaging, read receipts, apple pay, etc.)
Would love HN thoughts/feedback! We also have a customer facing version if you’re not a developer (https://usebalto.com/) and wrote a blog documenting the journey for those interested (https://usebalto.com/blog/balto-origin-story%20) :)