A colleague alerted me to a spamming tool available on the web at the following web URL:
It's a page that allows someone to enter in an email address and it will tell you whether or not that email address is live. In essence, this is the non-techy spammer way of checking for a valid RCPT TO address in the SMTP command. If it comes back positive, the email address is live, and if it comes back negative, the email address is not and therefore the spammer can remove it off their list.
How do I know it's a spam tool? Well, besides thinking of almost no legitimate uses for this web tool, the WHOIS information is suspicious. The registrant lives in Moldova but has a phone number registered to a North American address. Even if he screwed up and meant Maryland, the area code resolves to no actual area code in the United States.
The site was created in July, so it's fairly new. This in itself is not the clincher but combined with everything else, I think we can be rest assured that a spammer set up this page in order for himself (and possibly other spammers, I can't imagine why) to verify his spamming lists.