I've had quite a few similar emails and I don't even sell equipment (I get them because forklifts are discussed on my site). You need to ask yourself if there is any legitimate reason why someone from a distant country would want to purchase equipment from you and also look at the content of the request to see if there is enough detail to make you believe the person actually knows something about the equipment he is trying to purchase (the scammers usually don't, they just request whatever they see on your website). The vast majority of these are scams, but it may be possible there are some legitimate requests in there. If you think the request is legit, you need to set the payment terms in such a way that you can't get ripped off. If you're not familiar with international transactions, you need to stay clear of these.