Anybody have any pointers as to where to look for this oddity:

Message arrives, receives a spam score of -1.909, required is set to default 6.6, yet the message subject gets the SPAM flag added...

X-Virus-Scanned: amavisd-new at email2.....
X-Spam-Flag: NO
X-Spam-Score: -1.909
X-Spam-Status: No, score=-1.909 tagged_above=-10 required=6.6
tests=[BAYES_00=-1.9, HTML_MESSAGE=0.001, T_RP_MATCHES_RCVD=-0.01]
Subject: ***SPAM*** Ed off on Tuesday

This message itself is clearly not spam, and in fact originates on one of our other mail servers (not this particular instance of Zimbra.) I have confirmed that the previous server is *not* flagging this message - it occurs on this instance of ZCS.

It would be one thing to go searching if the score showed a spammy message, but in this case it is clearly ham at that stage too, so I'm a bit lost. Interestingly, this appears to be the only user whose messages get flagged this way...

Any thoughts?