To the cheers of Yahoo! users worldwide, the company has announced that it will begin blocking fake e-Bay and PayPal emails in an effort to reduce phishing scams directed against its users. The blocking technology - called DomainKeys - verifies the sending domain of the email and allows ISPs to block illegitimate messages. Yahoo! is rolling out the technology and expects to have it globally deployed within a few weeks.

Domain verification usually causes no small amount of grief because it relies on domain owners to have their reverse DNS lookups in good working order, something many domain owners overlook. Forward DNS lookups are easy. Administrators know right away whether they work or not. Reverse lookups aren't quite as polished, and since forward lookups work independently of reverse lookups, many domain owners go without reverse lookups in place.

As spam, phishing and other undesirable user-targeted activities increase, and diminish the performance of the overall system, reverse domain verification will become more important. DNSstuff.com has some good tools for performing reverse lookups, if you're unfamiliar with them or aren't sure that your domain(s) are up to snuff. DNS and BIND by O'Reilly is the gold standard for DNS how-to information. If you don't have a current copy, you may want to invest in one.