Mail In Black

Mail in Black is the name of a French company that provides an interesting anti-spam solution.  Their idea is simple.  Spam is generated by robots.  Thus, if you filter out every communication issued by robots, than you would get rid of spams.   How to detect a robot?  Apply a Turing test.


How does it work:

  • You define an initial white list of email addresses or domains.
  • When MailInBlack receives an email, it checks whether the emitter is part of the white list.  If it is the case, then the mail is forwarded to you.
  • If the emitter is not in the white list, MailInBlack returns, on your behalf, a captcha challenge (for instance, type the orange text). 


  • If the challenge is successful, then it forwards the message and automatically adds the recipient to the white list.
  • Else the message is quarantined and the emitter is added to a black list.
  • Of course, if you rescue a message from the quarantine, then the emitter moves to the white list.

According to me, there are some potential hiccups:

  • You may loose messages from automatic systems that are legitimate to receive (and there are many legitimate).  Therefore, the initial building of the white list is important.
  • Some surprised emitters may believe that the challenge is actually a spam or worse, a malware.  This is mitigated as they just sent you a message an d “you” ask the challenge.
  • If they are successful, how long will it take before we will we the first malware spam mimicking a MailInBlack challenge but with a malicious site?

Nevertheless, an interesting approach to anti-spam. 

One thought on “Mail In Black

Leave a Reply

Your email address will not be published. Required fields are marked *