We use a custom tool called setsa to determine whether your email should be run through SpamAssassin. To enable SpamAssassin for mail to your UNIX account, run
setsa on
To later disable it, run
setsa off
To check whether you've enabled it or not, run
setsa
You can similarly enable or disable SpamAssassin for a virtual mailbox address by adding it as the first argument to setsa; for example, setsa user@domain.com on enables SpamAssassin for user@domain.com if you have DomTool permissions for domain.com.
Please don't enable this if you can't commit to following the training procedure below when SpamAssassin makes an incorrect classification! SpamAssassin makes small mistakes over time, and this can interact poorly with its automatic learning of which message properties signify spam. If you don't correct its small misclassifications, then these increase the chance of misclassifying future messages, which itself leads to more faulty learning, vicious cycle style.