When using SpamSieve with Mailsmith, Mailsmith tags messages using the Is Spam and Is Not Spam properties. Although you can use Mailsmith’s Advanced Query feature to search on these properties, they are otherwise not visible in the user interface. Therefore, you should mark spam messages in a visible way, either by letting Mailsmith move them to a separate mailbox, or by setting up a filter to change the messages’ labels based on their Is Spam and Is Not Spam properties. Otherwise, you will not be able to correct SpamSieve’s mistakes to improve its accuracy.
In Mailsmith 2.2 (in public beta as of this writing), this is no longer a concern because Mailsmith automatically marks each message with its spam score, from 0 to 100.