Yeah, this sucks. I just upgraded to an m8 from an m7 YESTERDAY, and am VERY disappointed to discover that this feature has been removed, as I'd come to RELY upon it on my m7. I did a live chat with HTC last night, to make sure it didn't have to be enabled first or something, and they confirmed for me that it's been removed (though to be honest, the rep I was chatting with seemed kind of unsure himself. From reading here, it appears to be carrier-specific, as folks on T-Mobile & Sprint seem to have it). So I will now have to begin a search for an apk of the messaging app with the Secure Box feature intact... If anyone has it, or is aware of where I might be able to find it, please let me know. I've done some searches, and have found some threads that claim to have all Sense 6 apk's included, but I downloaded them, and checked inside the archive, and the Messages app wasn't there. Downloaded another one (specifically saying it was the Messages app. ...and a newer version than the one I have currently installed), but it wouldn't install. If you have any good leads, please respond!