I notice that there are some sites that scrape craiglist listings, and allow their user to email the emails scraped from craiglist only when the emails are not XXX@xxx.craiglist.org. Other non-CL emails are allowed to be emailed to directly from their websites. Users are asked to manually those emails with CL's domain. Is there any reason for them to do this? My guess is that CL will ban the website's domain from further emailing if CL sense a large number of emails from that domain.