Can Spammers Use Guerrilla Mail?

(October 7, 2007)

We have been asked what we do to prevent Guerrilla Mail from being used by spammers.

Here is the answer: Spammers need to send huge amounts of e-mails to a huge amount of addresses. Guerrilla Mail is pretty much useless for that purpose. The only way to send an e-mail from Guerrilla Mail is to reply to an e-mail. And the reply function is locked behind a Captcha feature.

In order for a spammer to use Guerrilla Mail, he would have to go to Guerrilla Mail, create a new e-mail address, and then send his spam e-mails to that Guerrilla Mail e-mail address. Then he would need to go back to Guerrilla Mail and reply to all those e-mails. That, of course, would only work if he had set the target e-mail address as From: address of the e-mail sent to Guerrilla Mail. And even so, there is still the Captcha feature for the spammer to get around.

Sounds a bit complicated and time consuming, doesn’t it? More so, when you realize that spammers use bot nets with thousands of zombie computers to send their spam to millions of recipients in a matter of minutes and hours.

So far Guerrilla Mail has created around 260,000 e-mail addresses and has received around 3 Million e-mails. 2.9 Million of those e-mails were not valid (= spam). Since we started Guerrilla Mail around a year ago, the relatively small number 3,863 e-mails have been sent as a reply to an incoming e-mail.

Bottom line: Spammers use mostly bot nets with zombie computers and open mail servers.

Still not convinced? Guerrilla Mail has been mentioned in a positive way by some respected sources such as and is listed in the category Internet/Abuse/Spam/Preventing/Temporary Addresses of the Open Directory Project.