I've tried many but eMailganizer is the best – eMailGanizer Pro Review

If you use folders for organizing and maintaining emails as documentation, then there is no better app than eMailganizer. It learns your filing preferences and you can allow it to provide suggested folders for each email. Because of this feature my time on email is reduced significantly. In fact, I often prefer eMailganizer to my desktop client because filing/organizing email is so much easier on it.
Review by Miguel Luna on eMailGanizer Pro.