I am intrigued by how these work..... One post from 23 Jan is taggged "new" whilst a post from 28 Jan is not. I thought perhaps it might be function of responses but one from 6 jan with no responses in tagged "new" as well.
We assumed 'New' represents a first message not yet read starting a thread. Having checked the 'Help' file - it was not very helpful ;D . It could also simple represent a message not yet read!
Let us watch the posts and see if we can work out the logic of it.