HKCU\Software\Microsoft\Inbox\Settings\OEM\(create if necessary) and edit/create the following DWORD:
SMSInboxThreadingDisabled=1
HKCU\Software\Microsoft\Inbox\Settings\OEM\(create if necessary) and edit/create the following DWORD:
HKLM\System\Inbox\RecipientAutoCompleteand set/change the following DWORD:
There are so many hidden settings in Windows Mobile 6.1 Standard Edition we could explore. I was playing with my HTC Snap when I found this one. Settings for camera capture sound volume! Try to reduce (I doubt you will increase the volume) to the value that suit your ear.