Correct, Spamassassin will not classify emails be default. But it does include a Bayesian classifier and tooling that can be used to train it with curated ham and spam emails. It does require extra steps to set this up and feed it selected maildirs (for example, exclude inbox, spam and trash for training ham).

https://spamassassin.apache.org/full/3.0.x/dist/doc/sa-learn... https://cwiki.apache.org/confluence/display/spamassassin/Bay...