Currently Being ModeratedNov 6, 2012 7:29 AM (in response to Ian Lancaster)
There are no settings to change that. However, when you select a message and delete it, it will go to the one on top. If you then select a message below that selection, the order of deleting will reverse like you want. Once done, it should stay that way until you change the deletion order again.
Note that I'm doing this in ML. Not sure if the behavior is the same in Lion.