The outspoken founder of Chinese e-commerce company Alibaba, Jack Ma, has thrown down a challenge to the world's global Internet giants and put future shareholders in their place as the firm filed for a US stock offer. In a memo sent to employees minutes before Alibaba filed documents to the US Securities and Exchange Commission for its initial public offering (IPO), Ma described the listing as a "filling station" on the way to future development, according to a copy of it posted by the respected magazine Caijing on its website. Alibaba declined to confirm the authenticity of the letter, but it was widely quoted by Chinese state media on Wednesday. Alibaba has more than 20,000 employees. "Fifteen years ago, Alibaba's 18 founders were determined to set up a global Internet company originated by Chinese people, with hopes it would become one of the world's top 10 Internet companies, a company which will exist for 102 years," he said -- a lifespan which would mean it existed in three different centuries. Alibaba is often described as China's version of Amazon or eBay, since it has elements of both those firms but suited to the domestic market. It took on eBay in China over a decade ago, essentially forcing the US company to retreat. It operates China's most popular e-shopping platform, Taobao, which is estimated to hold more than 90 percent of the online market for consumer-to-consumer transactions. The listing plans indicate Alibaba will raise at least $1 billion, but analysts say the offer could raise around $15 billion, putting it on par with Facebook's $16 billion IPO in 2012. "After listing, we will still maintain the principle of 'customers first, employees second and shareholders third'," Ma said. "We believe no matter how difficult the decision, in the past or still in the future, maintaining principles is the greatest respect and protection for the benefit of all," he added. A diminutive former English teacher, Ma set up Alibaba in 1999, convincing friends to fund him with $60,000 and picking a recognisable name with the aim of helping small firms "search for treasure" -- the meaning of "taobao" -- by selling through the Internet. Ma stepped down as Alibaba's chief executive officer last year but remains as chairman to provide strategic direction.