More to the point what does it mean to you, White feathers do mean different things to people, I allways advise ' what it means to you' is more important that what a books says etc. think and ponder what it means to you - plus what was the circumstances in which the feather was found, what is going on around the person there are a lot of thing to take into cosideration, before you tell someone what it means.
In the past I had black feathers posted to me, left at the edge of my path of my home, on the doorstep, outside my shop etc. some where tied some not. So it would depend on the circumstances