it really depends on your workflow and what you use your email for.
For project management, I like to keep a really controlled Inbox, so I can see just the new stuff coming in. When a new mail arrives, if it has not already been actioned by one of my filters or Gmail plugins (Streak and ActiveInbox), a quick scan of it decides its fate:
- does it need immediate reply? (rarely so): reply to that, assign it to a project (if applicable), mark as "ongoing" and Archive
- does it need the intervention of someone else in the team:
forward, assign, label as "assigned" and Archive
- can it wait?: mark as read, label as "later" and Archive
This way, you can keep your Inbox in check, while keeping all the important stuff, but out of your way.
That's how I use it, anyways