DownloadSquad also saiys:
"Litepost stands out with a number of unique features, including email tagging and rating, as well as interesting 'Who, What, When, Why' sorting methods with which, for example, you can sort by date first, then sender (or vice versa). You can also arbitrarily group messages together for any reason, solving one of the complaints of the message threading or conversation view that Gmail made popular."