1. An Email is between TWO OR MORE people!..That means TWO OR MORE drives have the email..the sender and receiver End-user PC!
2. The end-user PC get backed up ..So there are back up of those PCs
3. The End-use PC to not sent directly to each other..else both sender and all receiver would have to be on line at the same time...your “send” email goes to a server for your email account...that email server sends in to the server for the receiver email account..and when the receiver PC come on line is asks it own email server for any email for it....and both those email servers get backed up.
..bottom line its total bs..if your local pc hd crashing would wipe out your email that would mean you could delete that same email on your local pc and have it gone forever...it does not work that way..in both in good IT practice and by what the government is required by law to document all communication
On your last point I have an option with my email account to either leave it on the server when it’s downloaded to my computer or delete it. If I choose to have it deleted from Google’s server the only place it’s supposed to exist is on my computer and if I delete it it’s gone (yes Out can be recovered with special software provided extraordinary efforts were taken). Now I know Google still probably has a copy in their backups, but I don’t have acess to it. If the server data is wiped every 6 months as the IRS claims then it’s gone. I don’t believe the IRS claim.