Suspicious customer questions

[Rankinefile]

Received a curious email from a potential customer in the Netherlands asking a lot of unusual questions (for our typical customers) such as "What is the name of your credit card processing merchant you run your credit card charges" and "Do you work on the weekends", etc.  A few years ago fraud was attempted on our account from the Netherlands and I have been suspicious ever since.  These questions don't seem, well, normal.  Am I being too overly cautious/suspicious here? 

[Kenlar]

No, highly irregular. Caution why would a buyer care how u run ur business? Buyers would only care or should on care about the item for sale. I can only recommend sticking to questions on the item.

[Rankinefile]

A follow-up email confirmed today that this is definitely a scam.  It was the exact same email we received 2 years ago:

"Hello,
Thanks for your response. We've listed items we're interested and want to know if they're readily available in-stock in the quantities, I want you to reply back with the total cost, plus an Express quote, we also have a reliable shipper that help with pick-ups. Let me know the total quote first, maybe i can direct you to my shipper for a quote. Your utmost reply back with the total quote will be highly appreciated."

They then go on to order large quantities of our most expensive products (8 each this time; 12 each 2 years ago).

The final clue is the shipping address:

...ADDRESS FOR THE SHIPPING QUOTE:....

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It's a warehouse in Rotterdam.