An original and simple solution from BuzzeeMail

The solution is to handle separately two problems:

• 100% of spam blocked How ?
  Simply deny any email from an unknown sender !
  No training required.
  When you send an email to a new contact, your trusted contact list is automatically updated.
  
  This solution is more and more adopted by email solution providers, such as Hotmail, MSN, Yahoo, or software vendors as Qurb...
  But used by itself, it has a major drawback: the users needs to access their junk box and identify real emails between hundreds of junk emails. BuzzeeMail solution is very smart as it guarantees to lose no email.
• 0% False positive How ? Any email from an unknown contact is automatically stored as suspicious (no manual action, configuration or training required). The sender is warned that he must confirm he originated the email. This action must be performed only once. Email becomes trusted and appears in the inbox.

Why is this technique more efficient ? Spammers are not able to confirm individually every single email sent. (They are spamming by millions).