When I reply to a question on eBay Contact a Member, the emails show up both on my personal email (which is attached to my eBay account) and in the Messages section.
Alternatively, the buyer may have pulled your contact information. You should have received his as well, since this is always reciprocal.
For your personal email, you can ask your provider to Block all messages from this person.
You can't do this on eBay, but you can Delete them without reading them, although you have to open them to delete them. Annoying. You can Report the spammer to eBay.
