Google records everything and deletes nothing.
Google says - "Delete or recover deleted Gmail messages. When you delete a message, it stays in your Trash for 30 days. After that time, it will be permanently deleted from your account and can't be recovered."
As I mentioned before, my other half had deleted masses of gmails over years and years. Yes properly deleted from the bin etc. The best you can do.
A couple of years back, woke up one morning to find all those emails back in her Inbox. About 6+ years worth.
Not a happy bunny.
Biting the hand that feeds IT
