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

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.