The first project of the MSBL, the Email Blocklist (EBL), Has entered beta testing.

The EBL contains cryptographic hashes of email addresses that appear in spam emails so that spam recipients can contact the spammer. Most listed email addresses are at large free webmail sites, and were originally spotted in the Reply-to headers or messsage bodies of "Nigerian" 419 Advance Fee Fraud spam or other types of spam that use similar techniques.

For more information, see EBL.