Getting sensivity level msg while sending mail through c# code

we are using c# to send outlook mail activity.

but we are getting one pop up please select level public or confidential every time.

I tried to add below code but still not working.

OutlookNM.MailItem oMsg = (OutlookNM.MailItem)oApp.CreateItem(OutlookNM.OlItemType.olMailItem)           
                oMsg.Sensitivity = OutlookNM.OlSensitivity.olNormal

after adding the above line still I am getting same level popup.