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Which talks about Bayesian spam filters being incorporated into Moz mail from v1.3a onwards.
That functionality out of the box (or zip in the case of moz... i love being able to just unzip instead of install) alongside the already impressive image / popup filtering abilities might draw in quite a few new users, especially given how many users are quite vocal in their hate of spam mail and irritating advertising.
n.b. if this has already been posted then feel free to remove