The Sentinel Messaging system has been changed in February 2016, the most notable change is the addition of Sender Lists rather than the traditional adding an allow/block to the filters.
Prior to the filters going, messages are pre-scanned for IP reputation, and can get blocked prior to filters blocking these. This should be taken into consideration with creating filters.
* Note: A Group or Organization filter can be created that over-rides a higher order via the “ignore previous destination.”