Use Outlook's conversation view to arrange related messages into meaningful groups.
Outlook displays messages as they're received, but there are ways to rearrange messages. For instance, you can click the Subject or From title cell to group messages by the Subject or From text, respectively. Sometimes this quick fix is adequate, but sometimes it isn't because the subject text often changes and threads often have responses from more than just one person.
When things are a bit too complex for a quick sort, use conversation view, but don't stop at enabling the view. To take full advantage of the view, go a step further and apply the settings that will make the arrangement truly efficient.
To arrange messages by conversation, click the View tab and check the show As Conversation option in the Conversations group. Then, choose All Folders or This Folder. The differences are subtle, but Outlook identifies conversations with a small triangle to the left.
To get the most out of conversation view, apply one or more of the settings. To do so, click the Conversation Settings dropdown. Perhaps the setting that provides the most insight and coverage is the one passed over the most. Be sure to check the Show Messages From Other Folders option, even if all your mail is in the Inbox. That way, Outlook will display messages you sent and stored in the Sent folder. These messages are an important part of the conversation but otherwise omitted from this view.
The Show Senders Above Subject option won't add much to the view if your Inbox displays one-line headers. If you're using multi-line headers, this option reverses the order of the From and Subject columns.
The third option, Always Expand Conversations is another setting that most users will want to use. Otherwise, you might lose context while browsing.
By applying the first and third settings, you completely change the view. You can see at a glance that Mary initiated a particular thread and that I (Susan) responded. That's why you need to include that first setting. If you don't enable this setting, you'll see only the original message from Mary.
Many users don't bother to view Outlook threads as conversations because they don't seem to get too much from the arrangement. The problem is that they just don't go far enough-viewing messages as conversations can be helpful, but you won't always appreciate the real advantages unless you apply the appropriate settings to the conversation view.
A few extras
If you don't want to use conversation view, you don't have to. With a message open, you can click the Related dropdown in the Editing group to see a list of all messages related to the current one. This route won't provide the same flexibility, but it's handy if you want to avoid conversation view.
When using conversation view, consider positioning the reading pane to the right. Doing so is an efficient way to view all of the messages in the thread quickly. Outlook displays all of the messages in the Reading Pane regardless of its position, but viewing them on the right rather than below displays more text.
In addition, when working in conversation view, Outlook will apply many actions to all of the messages in the conversation, not just the current one. For instance, you can apply a category to a conversation by applying it to a single message. Later, when more messages in the conversation arrive, Outlook will automatically apply the same category to the incoming messages.