[subhobroto]

Are you in the U.S.? Which state?

You're trying to establish a chain of custody here. The only person who remotely cares about the forensic integrity of the message is the judge (and the jury if it's a jury trial) and it seems like an argument you would like to make is "this email came from Google's servers so we didn't tamper with it" - but the judge won't take your word for it, you will need Google to substantiate that and they won't unless it's a workspace account.

If it's a workspace account, then your org already has a retention policy.

So again, what problem are you trying to solve and in which jurisdiction?

[nickjj]

I'm in the US / NY, with a normal personal account.

I think the issue with localizing it to a specific state is oftentimes contracts or working agreements have jurisdiction locations that align with the company. In other words, it might not be in NY. It could be anywhere, including different countries.