I can't say whether your specific email is legit, but I do see chat forums online discussing being able to submit postmortem requests to Google (using that term

I can't say whether your specific email is legit, but I do see chat forums online discussing being able to submit postmortem requests to Google (using that terminology). If I read it correctly somebody would have had to send a request to Google and convince them to hand things over (say, with some legal documentation).