What we call this is customer relationship management. If you are just a stranger on the internet, what will the customer think about you? Nothing - all they know is your price and product and location.
Think of it like this - you have friends who sell things. When you want to buy those things, do you buy them from your friends, or from their competitors? Friends, of course.
Therefore, you want to become friends with as many customers as possible. If you are never meeting them, only emailing them, this is harder, but it is never impossible. What we call this in english is developing a rapport with your customers. The more you can find out about them personally, the more friendly you become. Try and learn about their culture, their family, where they live.
You could try reading the news about their country, or even finding out things by looking at the Country Profiles on Alibaba.
Some people won't like it if you start making small chat via the email, especially if you ask personally questions. However, you can be the one to be friendly first, but telling them something about you. For example, "I might not be checking my email this weekend, because I am visiting my newborn nephew in another province. However, if you urgently need to get in touch, feel free to call me on 0384954030303..."
This means two things - 1) - if the client wishes, they can talk about your nephew, and then you can ask them if they have kids, etc. You are slowly becoming friends, not just business partners 2) You are showing how committed you are to their business. You are telling them you are away, but because they are so important, they can still phone you.