Texts and Beeper rely on a service's publicly available access to bridge them to your universal inbox. When that option isn't available, they turn to backdoors and workarounds. That's what happened in Apple iMessage's case. To offer iMessage support, Beeper has a network of always-on Mac computers that are programmed to forward chats even to Android and Windows devices. Companies don't always approve of these methods, however, and when Beeper tried to hack its way into a simpler iMessage solution, Apple blocked it.

A couple of years after WhatsApp, Apple jumped into the game with iMessage—its obvious drawback, that senders and recipients had to be using iPhones, was overcome by integration with the standard SMS platform on those phones. If a recipient was not on iMessage or was offline, the message would revert to SMS.

Rich Communication Services is a reinvention of cellular messaging, a halfway house between the SMS ecosystem run by network operators and platforms like WhatsApp and iMessage. The wide-scale RCS rollout is being driven by Google as Android’s iMessage equivalent

The only messaging app that has been proven, by an independent authoritative agency, is Apple’s Messages app (which uses Apple’s iMessage protocol that is truly end to end encrypted, Apple cannot read any of your texts which means that no one can read any of your texts)