hi emansfield1, there are several Support articles basically asking and tackling the same/similar question, as an example have you seen these Support articles ? [[Thunderbird incorrectly places emails in junk folder]], [[Junk filter]], which talk about and explains marking and filtering junk in Thunderbird, and how it is connected to server type (IMAP/POP). if these can't help you solve your issue, revert and please tell a bit more about your operational environment, all in order to try to nail down the issue a bit more. All the best from Stockholm.