Conversation based grouping in Outlook similar to Gmail?

I'm not sure if it helps, but Outlook 2010 has a conversation-based view that includes sent messages.

I use these steps (from a post on the More Productive Now blog):

1. Switch to your Inbox.

2. From the main Outlook View menu

   1. In Outlook 2007: select Current View > Define Views.
   2. In Outlook 2003: select Arrange By > Current View > Define Views.

3. In the list of views, select the “Messages” line, then click the Copy button. In the resulting window, type “Messages By Conversation” for the name of the new view. Select the This folder, visible to everyone option. Click OK to close this window.

4. In the Customize window that’s now displayed, click the Group By button. Uncheck Automatically group according to arrangement. Set the Group items by drop-down list to Conversation. (Leave the option button set to Ascending.) Click OK to close this window.

5. Click the Sort button. Change the Sort items by drop-down value to Conversation Index. Change the option button to Descending. Click OK to close this window.

6. Click OK to close the Customize View window.

7. Click the Apply View button, and you’ll see your new view in action!

Outlook 2007 doesn't support this natively. If you can't upgrade, you could see if you're able to install an addin like Xobni, which has this type of functionality.

My solution to make Outlook 2003 more Gmail-like was a macro which moves all the items I send into my inbox. Then the conversation view contains the whole picture. I haven't tested the macro in Outlook 2007 but it is working for me in Outlook 2010.

Add the following code to your ThisOutlookSession using Visual Basic Editor.

Private SentMailFolder As Outlook.MAPIFolder
Private InboxFolder As Outlook.MAPIFolder

Private WithEvents SentMailItems As Outlook.Items

Public Sub Application_Startup()
    Set InboxFolder = Outlook.Session.GetDefaultFolder(olFolderInbox)
    Set SentMailFolder = Outlook.Session.GetDefaultFolder(olFolderSentMail)
    Set SentMailItems = SentMailFolder.Items

    MoveItemsOnStartup
End Sub

Private Sub SentMailItems_ItemAdd(ByVal item As Object)
    MoveSentItemToInbox item
End Sub

Private Sub MoveItemsOnStartup()
    While SentMailFolder.Items.Count > 0
        MoveSentItemToInbox SentMailFolder.Items(1)
    Wend
End Sub

Private Sub MoveSentItemToInbox(sentItem As Object)
    Dim shouldSave As Boolean

    shouldSave = True
    Select Case sentItem.MessageClass
        Case "IPM.Schedule.Meeting.Resp.Pos"
            shouldSave = False
        Case "IPM.Schedule.Meeting.Resp.Neg"
            shouldSave = False
        Case "IPM.Schedule.Meeting.Resp.Tent"
            shouldSave = False
    End Select

    If shouldSave = True Then
        sentItem.Move InboxFolder
    Else
        sentItem.Delete
    End If

End Sub