One of the main sources of email addresses spammers look to is the "whois record" for domain names. This record of ownership and contact information for domains will have a number of email addresses on it, for the purpose of business related to the domain. Because these are used for vital domain functions they must be valid and up to date addresses, and since the record is public, spammers are able to create programs which scan the whois record for email addresses and add them to their spam lists.

To combat this, there are a number of systems by which you can prevent the email addresses on the whois record from being used for spam, such as My Privacy. This system, a free service provided by easyDNS, allows you to create an email address for use on the whois record, which forwards to the actual account you use. What prevents this address from being used by spammers is a "challenge" mechanism. If an email is sent to it from anyone but an accredited registrar, a "challenge" email is sent to the sender and if it is not replied to, the email is not forwarded to you. Automated spam messages would not have someone replying to such challenges, and thus would not be passed through.