Google bowed yet another new feature in Gmail Labs on Thursday. Now users can view up to five separate in-boxes in their Gmail account.This is perhaps the most useful feature that Google has added to Gmail in recent memory.

I have five separate e-mail accounts (don't ask) that I filter through my Gmail account. This way, I only have to check one in-box to see all my different e-mails. So far, I've been using labels to filter my accounts so I can see which e-mails were sent to which account at a glance. The solution worked, but was clunky.

The new multiple in-boxes feature from Gmail is far, far better than that.

Go into Gmail Labs, enable the Multiple Inboxes feature, and then go to settings to manage it. The default view shows your main in-box, plus a set of your starred items and your e-mail drafts. Using Google's search modifiers, you can set it up to filter up to five separate in-boxes to show pretty much anything you want.

For example, I am attending Mobile World Congress in Barcelona later this month. I set up a filter for subject:MWC and set that as one of my in-boxes. Now, when I view my Gmail homescreen, I see all the e-mails with "MWC" in the subject line lumped together in one place. You can break out the different in-boxes pretty much any way you want to.

The possibilities for filtering are nearly endless. You also can set the number of e-mails that you see from each of the other accounts and place them in any order you wish.

Just for the heck of it, I decided to go to the HTML version of Gmail on my iPhone to see if the filters show up there. They don't.

Even so, this is a great way to help Gmail users who have multiple accounts better manage their in-boxes.