The check's in the mail at Stamps.com (NASDAQ:STMP). Shareholders are being rewarded with a 9% after-hours stock advance after the online postage specialist delivered healthy fourth-quarter results and a bright outlook for 2007.

In its latest quarter, Stamps.com earned $0.20 a share -- or $0.22 a share before stock-based compensation -- on a 21% spike in revenues.

The company that has successfully taken on metered mail giant Pitney Bowes (NASDAQ:PBI) and the U.S. Post Office, offering small businesses the ability to print their own postage from home, is working.

I'll admit it. I laughed at the model seven years ago. The deficits ran deep. Consumer adoption ran weak. But the climate has changed, and so has Stamps.com.

Even though the company derives more than half of its revenues from its flagship service, which allows folks to pay and print postage online, the real firecracker in the Stamps.com arsenal has been PhotoStamps.

Have you received a photographic stamp lately? Whether it's an engaged couple sending out wedding invitations with their mugs on the stamp, or a giddy kid gearing up for his bar mitzvah, the company is cashing in on the digital photography boom and consumers' appetite for customization.

Buyers will pay as much as $17.99 for a sheet of 20 photographic stamps. Sure, that would set you back just $7.80 at the post office without the personalized picture, but where's the fun in that? Stamps.com moved 464,000 sheets this past quarter, a 35% improvement over the final quarter of 2005.

PhotoStamps made up 32% of Stamps.com revenues during the holiday-spiked quarter. If you like Shutterfly's (NASDAQ:SFLY) story, you may like this one as well, as another way to play the wave of customized merchandise based around digital photography.

Things should get even better at Stamps.com in 2007. The company is looking for revenues to clock in between $90 million and $100 million. Stamps.com sees earnings lining up between $0.70 a share to $0.80 a share (or a dime per share more if you back out stock-based compensation). Can a growing e-commerce company really be trading for less than 20 times forward earnings? Indeed.

Keep an eye on this one. If growth holds up, it won't be long before a single share of Stamps.com will run you more than a single sheet of PhotoStamps.

Stamps.com is not a Rule Breakers recommendation, but it's the kind of stock that we like to unearth in the growth-stock newsletter service. Want to learn why? Check out David Gardner's full list of growth-happy picks as part of a free 30-day trial subscription to see if it's right for you.

Pitney Bowes is a Motley Fool Income Investor pick.

Longtime Fool contributor Rick Munarriz has never ordered customized stamps, though he has ordered photo Christmas cards from Shutterfly. He does not own shares in any of the companies mentioned in this story. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool's disclosure policy isn't easily licked.