As noted on Al Iverson's blog dul.ru has been set to "wildcard" status in DNS meaning it is effectively "listing the world;". It looks like the domain has been put up for sale.
Dial-up User List is a database for the dial-up users IP addresses. Addresses are provided by ISPs. The purpose of maintaining such a database is to provide technical possibility to recognize e-mail sent directly by dial-up users (thus by-passing ISPs mail server).
If you think your IP address should not be in dul.ru zone or it got there by mistake, contact you ISP. If your provider agrees with you, he can send us a mail to email@example.com , in this case your IP will be deleted from dul.ru zone.
Is the information on our site wrong or incomplete? You don't want us to monitor your blacklist? Or do you operate a similar blacklist? We would like to hear from you!