The easiest way to feed spamassassin with spam is:
spamassassin -r < message.txt
To revoke spam message use:
spamassassin -k < message.txt
If you use Bayes just execute:
sa-learn –showdots –mbox –spam spam-file
sa-learn –showdots –mbox –ham ham-file
Please note: don’t feed Bayes weith different mail streams or public spams. These method will mislead Bayes into believing certain tokens are spammy or hammy when they are not.