The Email Blocklist (EBL) contains email addresses used to receive responses to spam emails. These email addresses are sometimes called email drop boxes. The primary target of this blocklist is "Nigerian" 419 Advance Fee Fraud spam. The EBL also lists contact email addressees seen in other types of spam that use free webmail accounts as the main contact points.

The Problem with 419

419 spam is particularly difficult to block using IP- or domain-based blocklists. It is usually sent through mailservers that also send a great deal of non-spam email, which reliable IP-based blocklists do not block. Most 419 spam also lacks URLs, or contains only "camoflauge URLs" intended to make the spam email appear legtimate without providing a path back to the spammers. Other spammers use similar tactics, but the volume of 419 spam alone eclipses all the rest.

Pattern matching filters have thus far been the best defense against 419. These filters have grown increasingly sophisticated, but any pattern matching filter that catches spam also catches a certain amount of legitimate, non-spam email. Pattern matching filters also require significant amounts of computing resources, slowing email delivery.

A Solution

Most 419 spam relies upon contact email addresses and mobile (cell) telephone numbers to allow spam recipients to contact the spammer. The EBL blocklist lists these email addresses as one-way cryptographic hashes. To use it, you extract the Reply-to and message body email addresses from incoming email, hash those email addresses, and check the hashes against EBL. If the email address is listed, you can treat that email as spam with confidence. Pinpoint accuracy and near-zero false positives are expected.

The EBLis currently in beta testing. We especially need people in the following fields:

If you are interested in testing the blocklist, please contact us at