At a sufficiently high level, everything is old. However, for real products, the details matter a lot. Just because X is conceptually similar to Y does not mean

At a sufficiently high level, everything is old. However, for real products, the details matter a lot. Just because X is conceptually similar to Y does not mean that they are the same, or that the difference is unimportant. Threading has been around forever, but I don't think any other email client has Gmail's "conversation view" (I'm kind of surprised that nobody has copied it yet, actually).