One of the most secure methods to do this has been to use an existing Macbook computer, or a macOS VM, but they all require additional stuff to be set up and keep working.
It appears that Sunbird is virtualising all of that in the background. Not everything works 100% and we have not yet seen anyone using this with their own Apple ID account.
However the big issue to remember is that there is a provider now in the middle, and I'm wondering about that claim of E2EE. I'm not sure this can be end device to end device encryption, or is it pulling a 'Cloudflare' here. I can't see how else it does this.
Of course, this is an alpha app so it doesn’t work flawlessly. Lots of features are missing and things don’t work quite as expected. However, as a proof-of-concept, it is sound and shows Sunbird might be the real deal.
See
I am using Sunbird with iMessage for Android. It works.#
technology #
imessage #
android 
The just-announced Sunbird app is in the very early stages, but I can confirm it does actually work for using iMessage on Android.
