Marist College observes Barracuda Reputation to block known spam
sites: it has to protect itself due to the ever increasing amount of
spamming that is going on.  I know because I've had my postings
blocked.  :-)

Spammers gain control of computer systems because of short, easily-
guessed passwords, Microsoft development deficiencies, and the large
number of computer owners who don't apply regular maintenance.
Further, accounts on large systems in companies and universities are
readily compromised - not by sophisticated techniques, but simply by
asking the account owner for their password via even the most
primitive and obvious phishing emails.  (College faculty members are
the easiest game in phishing, by far accounting for the largest number
of accounts compromised: inverse relationship between "intelligent"
and "smart".)  This results in an honorable system becoming a
voluminous spam generator, and quickly ending up on spam site lists,
which most sites now observe in mail handling in their mail servers.
It's an endless problem.

   Richard Sims