Oh man, not case sensitive, NOOOOOO!!N

I’m busted I guess. Beep boop.

Well that was the quickest random result I had while searching on mobile. Just to pave the way at least :)

That image seems to be on stock image sites like this one. So it’s just an image. Didn’t see any version that is converted to an actual theme.

Well, those windows reminded me of this old VLC skin.

And no, not a bot. Just a random internet user.

Looks like the design of LCARS (Star trek).

So you may like this theme or similar to this one.

Other people already mentioned Roundcube and Snappymail, which are good options already.

There’s also Cypht if you want a different approach. It combines multiple accounts into same interface so you can have a unified inbox.