Yep, it does all the right things. All the "heavy lifting" here is done by the Nylas sync engine which works natively with Gmail labels, actions, search, etc. and those same semantics are exposed in N1.
We've spent almost 2 years building the sync technology, so it's very stable and flexible. You can check out the IMAP code here: https://github.com/nylas/sync-engine
Wow awesome. If this works entirely locally, this is something I've been looking for for a long time. I might wind up making command line utilities out of it. Or even apply for a Nylas job. Email is something I care about an awful lot.
If, on the other hand, this makes use of some Nylas-hosted server, I'm a bit bummed out, since this would mean all my data is transferred through Nylas servers.
Which is it? Or should I just bite the bullet and read the source?
It's both! Most users are fine with hosted infrastructure, so they don't need to run+maintain it themselves. But you totally can if you want. The code for the sync engine and API is here on GitHub: https://github.com/nylas/sync-engine
We're working on putting together a better doc that outlines how to set up the entire stack locally. Ideally this could even be a Docker container.
And N1 has some easy way of integrating with a locally hosted sync engine, spawning it at N1 startup, and shutting it down at N1 tear down? Or is it the sort of thing were I'll need to host my own infra running this sync engine, and then hand tweak some config file to connect to my infra instead of yours?
I don't think GMail exposes the "primary/social/forums/promotional" classification (which they call categories). However, there's a workaround: in the GMail web interface, type "category:promotions" (for example) in the top search bar, and an option will appear to create a filter that automatically applies a label to all emails matching this condition. (in this case we can make a "promotions" label.)
Then your label will appear in your desktop client. Kind of a hack but I did this for thunderbird and it works.
As for making a plugin that handles this automatically - I'm not sure it's even possible, but I'd love to be proven wrong!
On second thought, the initial setup doesn't really need a plugin so much as the way categories are displayed. Especially cool would be to have them as tabs like in the web interface: once you get used to them, you find them sorely missing in desktop clients. I always find it weird to have my personal, social, and "promotions" emails brutally mixed together.
Unfortunately Gmail doesn't expose updates/forms/promotional via IMAP, so we can't show those. But they probably wouldn't be that hard to add in a plugin... ;)
We've spent almost 2 years building the sync technology, so it's very stable and flexible. You can check out the IMAP code here: https://github.com/nylas/sync-engine