What's a Craigslist email system?

Question about email replies I get from Craigslist ad?

• I posted a couple ads on craigslist for things I am selling. I got two email replies sent to me but all that they each said in the email was the title of my ad. So I replied asking them if they are interested and a second later I get an email sent to me from Mail Delivery System and the email says it could not deliver my reply and an attachment also came with the email. Is this a scam? If I download the attachment will it be a virus? Are these real people interested and how can I write back to them? Thank you for your help! :)

• Answer:

  You got replies from "bots" which respond to 1,000 ads per day. They never reply to what you are selling. They just re-write your title words. Or they say "Do you still have the item?" and nothing more. Or they say "Remove it from CL because i want to buy it....." and then they try to cheat you. Some sellers are so tired of the scammers that they write in their ad "If you want me to read your email put this word (choose any word you want) in the Subject line of your reply". But it is easier to just delete any emails which are not responding directly to the thing you are selling.