We run updates every night, so I can assure you that all our servers are running the very latest and stable releases as provided by CPanel. Spamassassin is installed serverwide and so the default configuration will be very tolerant considering the fact that it has to cater several accounts hosted on the server. It only tags the emails as spam based on keywords, phrases, the mailserver and sender domain etc. Emails coming into each account is different, spam evolve everyday making it more and more difficult to catch and so the best way to counter it is to continuously tweak your spamassassin + spam filter combination according to the emails that you are getting. The sudden explosion of spam can also be attributed to your account being picked up by email harvesters.