As in other email apps, conversation view in Windows Mail groups all messages with the same topic into a single display. It’s handy for keeping track of long email threads with lots of contributors, but it’s not for everyone. Fortunately, it’s easy to turn off in Windows Mail.
Open Mail by clicking Start and then typing Mail. In the main window, click the Settings icon.
On the Settings pane, click Reading.
In the Reading settings, scroll all the way to the bottom and click Off for the “Show messages arranged by conversation” option.
That’s all you have to do. From this point on, messages with the same topic will no longer be grouped and instead will show up as individual messages in your mail folders.