Protecting Data from Leakage at the Email Recipient Level
You have probably heard the story of the hacking of Hillary Clinton's email account. To be brief, Hillary, while serving as Secretary of State, used a personal email account for official correspondence. This email was hacked by an unknown hacker, and the data ended up on the Wikileaks portal.
I will provide a detailed analysis of this situation in the chapter dedicated to email hacking, but here I want to draw attention to the following point: there were about 30,000 emails in the inbox, some of which had been stored for many years. Information in 65 emails was classified as "secret," and in 22 as "top secret."
The advice seems clear: you should delete emails rather than keep them for years. This is reasonable, but the problem is that this will work if you are hacked, but what should you do if your correspondent is hacked? A leak will occur even if you delete everything on your device.
Advice
Periodically delete emails that are stored in your inbox and have lost relevance.