http://SERVER:41080/brightmail/quarantine/viewMsgDetails.do?id=QMsgView-3;3-0
Simply altering the last numbers in the URL (3;3 to 4;4, eg.) shows other domain-users Spam-Mail without any authentication.
Confirmed with Version 6.0.0.100 and previous beta-versions.
Brightmails support is aware of the problem, but didn't bother to confirm the problem in the 6.0 final.
Thomas Springer -- Nach mir der Synflood.