[dools]

SMS is the only inter operable messaging standard. If you send a message from iMessage to someone with Android it goes via SMS.

[eru]

Well, it's inter-operable between mobile phones. But not between arbitrary devices in general. E-Mail is probably the closest to that ideal?

> If you send a message from iMessage to someone with Android it goes via SMS.

Interesting. I think there are some Android messaging apps that also fall back to SMS, but it's not a behaviour I would find particularly useful.