Thunderbird's own Junk Controls use the term "Junk" for messages it considers bad. Messages marked as "spam" or placed into a "spam" folder are being handled by something outside Thunderbird; this could be your email provider, your own security software or a service such as SpamAssassin. In short, nothing you do inside Thunderbird can affect the operation of an external process. It's usually productive to go to your email provider's website, log into your email account there, and look for "not spam" checkboxes or other whitelisting options. A few providers (yahoo comes to mind) appear not to offer any options to allow the user to decide for himself what is and isn't "spam". I don't know what's moving spam to Trash. I can't agree with your use of Trash as an archiving function, but that's by the by. Rather than asking for Spam to go into the Junk folder (again this may require a visit to the website to set this up, if actually possible) another approach is to use a Saved Search folder to aggregate all your different storage locations for spam/junk into one virtual folder. If you can filter for a "spam" label (Saved Searches are based on filtering), this could include the Trash folder(s) for the spammy items that escape there.