AT&T HTC One M9 and M8 are finally being updated to Android Marshmallow (starting tomorrow)
Now, Mo Versi, Vice President of Product Management at HTC, revealed that the wait is about to end. Starting tomorrow, May 12, Android Marshmallow will be available over the air to the AT&T One M9 and One M8 (though it's possible that not all users will receive the update on the same day). As always, you'll be able to manually check if the update is available by going to Settings -> About -> Software updates on your device.
source: Mo Versi (Twitter)
Things that are NOT allowed: