11 April 2008 - "One of the biggest spam block lists on the internet suffered an embarrassing technical cock-up today which blocked emails from some servers at web security monitoring firm MessageLabs
and at some ISPs for about five hours. The CBL (Composite Blocking List), a DNS blacklist that takes its source data from very large spamtraps and lists IP addresses of open proxies and worms/viruses, said on its website that a problem in a contributory feed spat out a number of invalid lists... A spokeswoman at MessageLabs told The Register that others were affected by yesterday's false positive
. According to “word on the street”, Microsoft's Hotmail was also blocked
from sending email from some of its servers for a large part of the day, she said..."