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