Yeah in hindsight it's obvious I should've mentioned this category, but as I mentioned in the article, I strongly prefer my email apps to be unified (i.e. both Mac + iOS available) and there are fewer and less interesting (IMO) Mac-only apps than iOS-only apps. Postbox is great if you're just looking for a stable, no-frills client that's desktop-only. I also use Mailplane sometimes (it's basically just a tabbed wrapper around the Gmail web interface).