If you belong to any message lists, you know that it can be hard to follow message threads. Outlook supports sorting messages in many different ways. One of these, sorting by conversation topic, can help quite a bit. To sort in this way, go to the folder you want to sort. Then, click on View > Current View > By Conversation Topic:
When you do this, it may remove the Preview Pane, if you had that active. To get it back, click on View > Preview Pane. Sorting by conversation topic groups all e-mail for that folder according to their subject line. That way, you can keep better track of message threads you are reading. Also, you can delete an entire thread, which can reduce clutter and save time.
When sorting in this way, your folder will look like this:
To view messages, click the 'plus' sign next to the subject. This will expand out that thread so you can view the individual messages.