How do we see WHY a message was tagged as spam?

I’m pretty sure I’ve seen some documentation about this, but I couldn’t find it in the FAQ.

I had to get rid of Outlook 2011 because it repeatedly corrupted my Address Book database (destroying it beyond repair; look out for this defect, which apparently dates back to at least Entourage in 2008).

I reloaded my contacts from Vcards and switched back to Mail.

Turns out that a good portion of the next day’s E-mails were inexplicably dumped into the Spam folder, causing me some serious strife at home. We’re talking about E-mails from addresses that have long (and regularly) made it through safely. Some were in my contacts and some were not, but the ones that weren’t were not in there before the Outlook fiasco either.

So I need to determine why these messages were dumped as spam. How can I do this? Thanks.

kind of moot
OK, the Lion upgrade must’ve blown away the SpamSieve plug-in from Mail. Without the plug-in, the rule that you set up for SpamSieve sends every message to Spam.

BEWARE, FOLKS.

That’s what the Open Log command is for. In this case, since the plug-in was not installed (as described on the Lion Compatibility page), the messages would go to the Spam mailbox without consulting SpamSieve, so they would not appear in the log at all.