Warning from eBay:

[D. Bergin]

Yup, as everybody else says, the bots pick it up.

It's getting harder and harder to even send legitimate messages through Ebay without getting a warning.

Just somebody asking a general question about an item you have up for auction, and you have to be careful not to reference your website, any other sites that might have information for them on that item, your contact info, anybody else's contact info that might help them corroborate information.

If it's somebody I've done business with before, I usually just look for a Paypal e-mail address on file to respond to them properly.