回答:
もちろん、次のVBAマクロを使用して簡単に目的の結果を得ることができます。
Public Sub Application_ItemSend(ByVal Item As Object, Cancel As Boolean)
On Error Resume Next
If InStr(Item.Body, "(Client Name)") Then
If MsgBox("Are you sure to send this message?", vbYesNo + vbQuestion + vbMsgBoxSetForeground, "Message Text Warning") = vbNo Then
Cancel = True
End If
End If
End Sub