How can I approach new customers oversea?

I am a trainee working in a Malaysia water filtration company.The company only sold their products in domestic before.Now they want to expand their business oversea.My supervisors ask me to find potential customers' email on the internet and send the introduction letters to them bcuz it's free. But the result so far is not quiet good... i havn't got any respond yet.Beside that way, how can i approch more oversea customers on internet? thank you!!