I was never satisfied with their layout either. Always liked the way it behaved though. Ended up switching to Postbox, a Thunderbird fork, about 7 years ago and

I was never satisfied with their layout either. Always liked the way it behaved though. Ended up switching to Postbox, a Thunderbird fork, about 7 years ago and haven't really looked back. You have to pay for it, but it's a pretty solid email experience for what you pay (I think I paid $40 for a lifetime license a few years ago).