Email Zero is the term used to describe an empty inbox, something most professionals pursue every day. Without constant attention, it's natural for your inbox to become some sort of todo list, but compared ot a proper todo list your inbox does a pretty average job. So I thought I'd list a few of the things I've learned which help reduce the noise to something more manageable.
a proper provider
It's my opinion that you really need a proper email service, like a managed exchange server or a managed solution like fastmail. Gmail and other free services are problematic for privacy reasons. Self hosted solutions either require an inordinate amount of time to manage and maintain or else they quickly become unreliable. Our office uses fastmail because it's a cost effective bullet proof solution.
proper spam detection
Fastmail's in house spam detection is a little lack lustre, as are solutions offered by exchange servers. I don't really know, but I suspect that in both cases they lack the volume of email to properly learn what is and isn't spam.
Recently I've started using mxguarddog as a spam filter and it works pretty well. There service acts as an intermediary, so if my domain is wht.cr, then my mail server mx.wht.cr points to an mxguarddog mail server, which filters spam and forwards the rest to fastmail's mail server.
To tame an unruly inbox, powerful rule based actions are an absolute necessity. Gmail, fastmail, and exchange filters are fairly limited. I've been using mailgrace for a more robust solution. It works via an IMAP connection, so mailgrace gets notified when email arrives in a given folder, and triggers the rule based processing you've set up. They allow very complex filters, actions, and list based detection as well.