Is there a way in Outlook to figure out what rule, policy, or whatever caused an email to get put in the Junk folder? Can I right-click on an email and find this out in one of the options?
Some MTAs insert special headers into email messages that retain a 'score' on how 'spam-like' the message is based upon various metrics. Outlook sometimes uses these headers to filter Junk messages. You can see if any of these headers are seat (and what they are set to) by right-clicking on the message, selecting 'Options' and looking for the 'Internet Headers' section (Technically not what they really are, but it's what they are labeled as in Outlook :( ).