Outlook Rule for MailItem Work

' Starting with Outlook 2002, you can call a VBA subroutine from a Rules Wizard rule using the "run a script" rule action.

Sub ConvertToPlain(MyMail As MailItem)
    Dim strID As String
    Dim objMail As Outlook.MailItem

    strID = MyMail.EntryID
    Set objMail = Application.Session.GetItemFromID(strID)
    objMail.BodyFormat = olFormatPlain
    objMail.Save

    Set objMail = Nothing
End Sub