Thunderbird does not have a true white list or black list. Instead, it works with a filtering process, defined at https://support.mozilla.org/en-US/kb/thunderbird-and-junk-spam-messages This is a good long-term solution, but does not help with onslaughts of spam. If you are receiving spam from known source, I suggest creating filters to manage them, or consider using a third-party spam tool, or check to see if your email provider offers such.