you will can download the game when alpha open read ur email !!
I read the mail more than three times for the exact same reason.
There is no information about when we can download the game. Best thing we get is: "The Closed technical Alpha will open Thursday July 12th 3PM CEST"
I bet you are right, but still there is no reason to be cocky, especially when you are wrong about the mail.
I saw this on my Twitter feed this morning:
If you were lucky enough to get into the Closed Technical Alpha for Insurgency: Sandstorm please be aware there is no preloading on #Steam the download will become available when the CTA launches. Please see the email you revived for details and ensure you are aware of the NDA
I think it's clear that it will be become available to download when the CTA starts tomorrow.