By default, Outlook Web App 2010 will group messages and replies into Conversation threads. If you would like your mail folders to be sorted in the traditional list view, follow the steps below:
1. Log on to Outlook Web App at https://na02.msexchangeoutlook.com
2. Click on Conversation by Date above the message list pane.
3. Under the Conversations category in the drop-down menu, click off.