University of California, Riverside

C&C Antispam

Realtime Blocking Lists

What are Realtime Blocking Lists?

Real Time Blocking Lists (RBLs) are lists of known e-mail sites that generate spam. RBLs are utilized by UCR's e-mail system and are updated frequently and dynamically (without human intervention) as new spam generating sites are discovered (RBLs thus function like the anti-virus software running on the campus e-mail server). If an e-mail message comes to campus from a site on the RBL, it is simply returned to the sender. The message is not tagged and it never makes its way to campus e-mail inboxes.

Importantly, RBLs do not replace spam tagging. Rather, RBLs are meant to complement campus spam tagging. C&C's goal is to limit spam mail to the greatest extent possible via a combination of anti-spam services and initiatives.

Which RBL is the Campus Using?

UCR has partnered closely with University of California, Irvine (UCI) in the selection of an RBL source. Both UCI and UCR have decided to use Spamhaus RBLs (please visit

C&C has utilized the Spamhaus RBLs on a test e-mail server and the results were impressive. The RBL  blocked up to 90% of spam that was not tagged by the campus anti-spam system. Moreover, C&C did not experience a single "false positive" during the testing process.

UCI began using its Spamhaus RBL in early 2005. They are reporting only positive feedback concerning this new service. Students, in particular, are grateful that disk quotas are not being "filled up" with messages tagged as spam.

Problems with RBLs

Although highly improbable, it is possible for someone to send legitimate e-mail from a site identified as a spammer (by the Spamhaus RBL). C&C feels this is unlikely given UCI's positive experience with RBLs, C&C's testing, and Spamhaus' reputation for conservatively maintaining its RBLs.

Nevertheless, if you feel a legitimate message has been blocked by an RBL, please e-mail the Help Desk ( and C&C will investigate the issue immediately. If an e-mail site has been misidentified as a spammer, C&C will quickly remove the site from the RBL.

Please note that the RBL service only applies to e-mail accounts on the central campus mail server or to e-mail addressed to addresses.

Questions, Comments, Feedback

RBLs are only one of several new anti-spam initiatives deployed during the Fall quarter 2005. C&C welcomes questions, comments, of feedback concerning the RBL service, the campus spam tagging system, or any other e-mail related service or support provided by C&C. Please e-mail these questions, comments, or feedback to Phyllis Franco (, Manager, Computer Support Group.

More Information 

General Campus Information

University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

Department Information

Computing & Communications
Computing & Communications Bldg.

Tel: (951) 827-4741
Fax: (951) 827-4541