[Goose]

This may approach the Terry rule in the minds of some, but the real question comes down to what expectation of privacy an email confers on those who sent it and those who receive it. We do know for example that emails sent to/by government are often, but not always, available via FOIA lawsuits. Other emails have different levels of privacy attached to them, but these levels are a bit undefined. The problem of third parties disclosing emails that they  possess electronically or in hard copy cannot, IMHO, be solved. The only realistic and fully effective solution is to admit there is NO expectation of privacy. Whatever you say in an email is public. If you want to say something in an email that you do not want to be public, encrypt the email. The recipients who can decode the email are now responsible for its physical security. They know it is sensitive or else you wouldn't have encrypted it. Third parties can't leak/use/reveal it because they can't read it. No other solution really works.
Realistically, anything that goes over the internet passes through the "hands" of many other people. Most things that are transmitted electronically even on a private LAN have the same problem. At a minimum, the IT folks can access it all. Some of those people may intercept and divulge what was transmitted. You  may not even know/can't prove who did it. Even if you do, they may be outside of your jurisdiction and not subject to legal sanction. On top of that, it is often true that somebody knowing what an email contains may allow them to damage you without making the email public. They can act on what they know without revealing anything at all about how they know it. Given that, you just have to realize it is public and behave accordingly.

[Goose]

This may approach the Terry rule in the minds of some, but the real question comes down to what expectation of privacy an email confers on those who sent it and those who receive it. We do know for example that emails sent to/by government are often, but not always, available via FOIA lawsuits. Other emails have different levels of privacy attached to them, but these levels are a bit undefined. The problem of third parties disclosing emails that they  possess electronically or in hard copy cannot, IMHO, be solved. The only realistic and fully effective solution is to admit there is NO expectation of privacy. Whatever you say in an email is public. If you want to say something in an email that you do not want to be public, encrypt the email. The recipients who can decode the email are now responsible for its physical security. They know it is sensitive or else you wouldn't have encrypted it. Third parties can't leak/use/reveal it because they can't read it. No other solution really works.
Realistically, anything that goes over the internet passes through the "hands" of many other people. Most things that are transmitted electronically even on a private LAN have the same problem. At a minimum, the IT folks can access it all. Some of those people may intercept and divulge what was transmitted. You  may not even know/can't prove who did it. Even if you do, they may be outside of your jurisdiction and not subject to legal sanction. On top of that, it is often true that somebody knowing what an email contains may allow them to damage you without making the email public. They can act on what they know without revealing anything at all about how they know it. Given that, you just have to realize it is public and behave accordingly.