Posted this earlier. I believe this is the email you get when you buy a new phone. Correct me if I am wrong but I believe you get this after new IMEI and sim are attached to your account and the upgrade process is complete. Searched through my emails and see all my old ones for all my devices.
Hmm Ive upgraded before and I have never seen that
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I remember one year I never got a tracking number and on launch day while on the phone with att, being told i wasn't going to receive it, it showed up at my door