For the past few weeks (since I reached Inbox Zero), I found one of the easiest ways to manage my email (and my day) is to replace my inbox with two folders: Colleagues and Non-Colleagues.
Here's what my mail looks like right now (yes, I'm a bit behind):
These inboxes are accomplished using three fairly simple smart folders. If you want to give it a try, follow the instructions and screenshots below:
First, create a smart folder called "Colleagues (ALL)" and enter all the domain names of your colleagues. This smart folder will show you ALL mail from your colleagues, even mail outside of your inbox.
Then create a smart folder called "Colleagues" that looks at your "Colleagues (ALL)" smart mailbox. But then set the filter to only show you mail that's in your INBOX.
Next, create another smart mailbox and call it "Non-Colleagues". Set the filter on this one to show you ALL mail in your inbox that DOES NOT exist in your "Colleagues (ALL)" smart mailbox. Essentially, this mailbox shows you everything that's left over.