It used to be, come mid-November, the catalogs would start to pour into our homes at a distressing rate. One would think of the poor mail carriers schlepping pounds of recycling from trucks to houses. Now the flood is also electronic. The commercial e-mail offers start to pour in even more than at other times of the year. As with the printed catalogs, some you want, most you don't. But which You don't want the Macys spam until you desperately need to buy a sweater for your dad, and, of course, there's a coupon for that in your inbox. Except you don't want it in your inbox. You want it out of the way.

So you can't delete the BACN, and there's no way to keep up with filing it or managing filters to do it for you. OtherInBox, though, has finally come up with a solid, useful, and free solution for managing the influx of semi-wanted email.

The product, OtherInBox Organizer, simply files e-mail from known commercial sources into subfolders. It works in Gmail and Yahoo at the moment. To be sure, this is nothing that you couldn't do with filters you set up yourself. The beauty of Organizer is that you don't have to do any of that work. The Web service knows where to send e-mails, with very good accuracy. I tired it, and e-mails from my bank are now going to the "Finance" folder and coupons from Macys are going where I want: "Shopping."

Getting started in OtherInBox is a straightforward exercising in reviewing the service&39's automatic filter settings.

(OtherInBox's previous app, Defender, required users to give commercial e-mail senders a new e-mail address, like "Macys@rafen.otherinbox.com." That was too much work, and the product did not get traction.)

My brief review: The Organizer service is just great. After a few minutes to tune its filters to my preferences (for example, I created a new sub-folder for tech-related emails from Dell, Apple, etc.), I turned it on and it auto-filed more than 10,000 emails from my previously unmanaged Gmail inbox that had about 33,000 messages in it. It's kept up with new mail, too, alerting me when it sees a new sender that it can handle for me.

OIB can also provide a calendar feed of when packages you're ordered are due to arrive. Future services may include services like automatically deleting coupons that have expired.

But is there a business in providing such a useful service for free As CEO Joshua Baer explains it, there is, and it's very clever. "We want to be the Neilsen ratings of email," Baer says.

OtherInBox Organizer auto-files commercial messages in subfolders in GMail (shown) and Yahoo mail.

Here's how that can work: All the OtherInBox products and services (there are more coming) work on consumers' e-mail accounts. Once you hook an OIB service into your inbox, not only does OIB know what it's doing with your e-mail, it knows what you're doing with it, and it knows it not just for an individual sender, but for entire categories of senders.

"We can tell marketers what's happening across brands," Baer says. OIB knows which messages are opened, read, deleted, filed, and so on. It knows which e-mails are receipts and package tracking notes, so it knows what people are buying and where things are being sent. The service could collect huge amounts of aggregate shopping behavior data that's well beyond what individual e-mail marketing services can provide, because e-mail sending engines only tell their customers what's happening in their own campaigns. OIB knows what happens across all of them. And that data is what OIB sells to marketers. All OIB has to do to get quality data is keep its consumer-facing services useful and free.

At this point, though, you're probably getting nervous about the potential for a privacy or security catastrophe. Baer says, "We're taking small steps" in the collecting and analysis the data. He wants to be sure OIB never reveals personally identifiable information to his marketer customers. That's going to be a technical challenge, but at least I'm convinced that Baer understands that his whole company collapses if he fails at it.

Baer thinks his e-mail behavior analysis service becomes a workable business when OtherInbox gets to about 2 million users. At the moment it's got 500,000. Watch this company--it's a mover.

See also my Reporters' Roundtable interview on the future of e-mail, with Joshua Baer and Altimeter's Charlene Li: