Heya, I'm the PM for Nylas. We have a Mac mail client called Nylas Mail that's totally free that we launched on HN a couple of months ago: https://news.ycombinator.com/item?id=13417616
Happy to answer questions about it if you have any -
(And, yes, we are working on getting Windows and Linux out - even though it's an Electron app, there's a lot of platform specific stuff we need to do so that it doesn't go all T Rex on your memory and CPU.)
* Any plans to offer an app to purchase vs subscription model? I need support for Exchange and rules but can't justify the monthly price tag
* Is the app downloading the messages directly or do you store them on your server? From your website, it implies the latter.
* No plan for a one-off purchase option at this time.
* Nylas Pro (formerly N1) stores messages on the server; the new Nylas Mail downloads directly to the client.
Mailplane has been my go-to--it's basically a native wrapper around Gmail, but has integration with a number of popular Mac apps and native-style keyboard shortcuts and easy account switching if, like me, you have multiple GApps/GSuite logins.
Kiwi is similar, but doesn't have quite the level of integration Mailplane does although it has a more modern interface.
That said, I missed extension interoperability with Gmail enough that I largely just access the Gmail website directly through Chrome or Safari now.
I also use Spark, I love everything except their "Compose a new email" button. To me personally it is a bit hidden. But as I mostly respond to mails, it's not that big of a problem to me.
Btw tags never worked for me anyway, but Spark has cool functions regarding bringing the really important (personal) mails to your attention. Also, their function not to jump to the next mail when you finish reading one is brilliant. I hate accidentally opening a mail I don't intend to read at the moment and then having to mark it as unread.
I've been using Airmail for about 2 years now and I like the markdown mode.
But right now, I'm testing both Polymail and Nylas because they both have these specific features that Airmail lacks (and that are deal-breakers for me):