Here are a few ideas from the experts:
Security and privacy settings enable Thunderbird to control spam.
Bayesian filtering analyzes the content of an email message and computes a probability of whether it is spam or a legitimate message.
Training the adaptive filter in Thunderbird is easy. You simply turn on junk mail controls and classify your incoming email as either junk or not junk.
Thunderbird maintains the capability to have a white list of acceptable email senders. Those senders are never subjected to the Thunderbird junk mail scanning.
A special server-side account, usually named catchall, can be used to enhance the junk mail filter list.