FiftyOne is one of those under-the-radar companies VCs like to mention when I ask who’s killing it in ecommerce these days.

That wasn’t always the case — FiftyOne has gone through several iterations, since it got its start as a foreign exchange company in 1999. It had amassed $24 million in VC backing before pivoting to its current business model in 2007. The company raised $5 million more, launched the current iteration of its international ecommerce logistics tools, and set about “killing it.”

Today FiftyOne has gathered another $10.1 million according to an SEC filing. The total offering amount listed is “indefinite,” so the round is likely to close even higher. Prior investors include Seyen Capital, Pitango Venture Capital, and Delta Ventures.

FiftyOne solves an acute problem in the ecommerce world. International shipping is expensive and messy. Products can take days to clear customs. Sites aren’t optimized for international shoppers, and shipping costs make it an unappealing option.

But there is a strong demand for American brands, particularly in English-speaking countries like Canada, Australia, and the UK. CEO Michael DeSimone gave me the example of True Religion, the US denim company, charging a $50 try-on fee in Australia, where high prices on American-brand denim have shoppers trying on jeans in the stores so they can buy online. FiftyOne helps brands sell to 106 countries. Many sites that don’t even sell internationally still receive a big chunk of traffic from overseas. FiftyOne helps them capitalize on that.

Clients include Charming Shoppes, Gilt, Sears, Under Armour, Williams Sonoma, Macy’s, J. Crew, and CB2.

The company had around $140 million in gross merchandise sales last year and has a $200 million run rate for 2012. It earned around $40 million in revenue on those sales and is profitable with 100 employees. The company continues to re-invest profits. Earlier this year FiftyOne acquired Borderfree, a Canadian ecommerce logistics company.

In 2013, it’ll launch a self-service model, which will allow retailers to do international shipping seamlessly. The company is also developing a customer engagement strategy that helps localize ecommerce sites as much as possible, including automatic geolocation and prices that show up in local currencies. FiftyOne may eventually host and manage local sites for merchants in foreign countries as well — it already does so on Alibaba, China’s virtual shopping mall.