Auto Respond for new Classified ad website

I have started a brand new classified ad website in a my local city. I'm looking for a way to send a email to anybody in my area that posts an ad on craigs list, The email will be simple and let them know there is a new classified ad website in our city and to give it a try! I need a effecient way to do this without having emails being blocked. I'm not trying to send a ton of emails a day so not to get blocked. I have a VPS with full control to set this up with the right person!