One of our mailboxes is receiving mail that has been flagged as spam, example:

X-Spam-Flag: YES
X-Spam-Score: 9.04
X-Spam-Level: *********
X-Spam-Status: Yes, score=9.04 tagged_above=-10 required=4
tests=[BAYES_99=3.5, HTML_IMAGE_ONLY_24=1.552,
HTML_IMAGE_RATIO_02=0.383, HTML_MESSAGE=0.001,
MIME_HEADER_CTYPE_ONLY=0.56, MIME_HTML_ONLY=1.457,
SUBJECT_NEEDS_ENCODING=0.001, SUBJ_ILLEGAL_CHARS=1.586]

This message was delivered to the user's mailbox, even though it's way beyond the required score (and was flagged as spam). Any ideas/suggestions on what would cause that to still deliver?