or spam probability to messages that are not bluelisted or greenlisted . being able to use IMAP mailboxes to update server-side filters. For example: Train Bayesian classifiers by putting “ false negatives ” and “ false positives ” into IMAP mailboxes named, for example, +This-was-tagged-as-non-spam-but-actually-THIS-IS-SPAM and +This-was-tagged-as-spam-but-actually-THIS-IS-NOT-SPAM , respectively. This type