Wirelessly posted (Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 8.12; MSIEMobile6.0) Sprint Touch Pro 2)

try this but i think it only works for sprint...
No SMS sent notification
(HKLM\Software\Microsoft\Inbox\Settings\SMSNoSentM sg=1).

then try this 1, go to settings/personal tab/sounds & notifications/event:MESSAGING:NEW TEXT MESSAGE Then deselect "DISPLAY MESSAGE ON SCREEN"

thats how i got rid of the message sent sound and stopped it from showin the popup at the bottom of the screen on mine. now mine only plays my msg tone and only the little msg icon shows up at the top of the screen and thats all. hope that helps you.