Sub Macro1()
Dim oRng As Range
Dim oWord As Range
    Set oRng = ActiveDocument.Range
    With oRng.Find
        Do While .Execute(FindText:="_")
            Set oWord = oRng.Duplicate
            If oWord.Words(1).Start <> ActiveDocument.Range.Start Then
                oWord.MoveStartUntil Chr(32), wdBackward
                oWord.MoveEndUntil Chr(32) & Chr(13)
                If InStr(1, oWord.Text, "@") = 0 Then oRng.Text = " "
            End If
            oRng.Collapse 0
        Loop
    End With
lbl_Exit:
    Set oRng = Nothing
    Set oWord = Nothing
    Exit Sub
End Sub