How can I modify conversationTopic so emails with different subjects are put in the same thread?

Question

I want to help Outlook 2010 thread my emails. My understanding is that it bases the conversation view off of the conversationTopic property of the MailIte

Answer 1

Using Outlook Redemption, I was able to merge selected Mail Items into a single conversation with the following code. I modeled it off of @fredless's answer above for my needs.

Public Sub MergeConversations()

Dim NewConversationTopic As String
Dim msg As MailItem
Dim msgSel As Selection
Dim oRDOSess, oNS, objRDOitem As Object

Set msgSel = Nothing
Set msgSel = Application.ActiveExplorer.Selection

If msgSel.Count <= 1 Then
   MsgBox ("Multiple Mail Items have not been selected!")
   Set msgSel = Nothing
   Exit Sub
End If

Set msg = msgSel.Item(1)

NewConversationTopic = msg.ConversationTopic

Set msg = Nothing

Set oRDOSess = CreateObject("Redemption.RDOSession")
Set oNS = Nothing
Set oNS = Outlook.GetNamespace("MAPI")
oNS.Logon
oRDOSess.MAPIOBJECT = oNS.MAPIOBJECT

For Each msg In msgSel
   Set objRDOitem = oRDOSess.GetMessageFromID(msg.EntryID, msg.Parent.StoreID)
   objRDOitem.ConversationTopic = NewConversationTopic

'the following line is from this answer

   objRDOitem.Fields("http://schemas.microsoft.com/mapi/proptag/0x00710102") = Null
   objRDOitem.Save
   Set objRDOitem = Nothing
Next msg

Set msgSel = Nothing
Set msg = Nothing

End Sub