I believe Craigslist is now using their email relay service for all emails so buyers and sellers don't reveal their email addresses to each other.
I have sold a fair bit through Craigslist with few problems. I have seen buyers who seem really interested just quit responding to email. I have more problems with sellers who never respond to repeated emails when you want to buy something. In some cases I have used different email addresses in case one address is marked as spam.