Mozilla Mail has junk-mail classification. With some initial “training” the client can identify and segregate spam messages from good messages. To see more about Mozilla’s junk-mail classification, visit the Mozilla Spam Filtering page.
Whatttayaknow, it actually works. The UI was a little confusing at first. The first time it runs, it seems to flag all the messages with a little junk icon. At least it looks like a junk icon with the default skin. Once I installed the Orbit 3+1 skin, I could tell that there was a little question mark. Once you get it straight on what is and isn’t spam, it starts working its magic. Its caught 6-7 spam messages so far. No telling how it does with false positives though, because I haven’t gotten any legitimate mail since installing it. You can see why I am so happy to have a smart spam-filter.