One man's look at email confidentiality

This article by Dan Polansky looks at email confidentiality. Initial questions:

Under what circumstances is email content confidential?
Is there a legal requirement to maintain email confidentiality?
Is there a moral requirement to maintain email confidentiality?
Is the fact that an email with title so-and-so was received from person so-and-so confidential?
Is the fact that some email was received from person so-and-so confidential?
Does confidentiality, when it applies, protect every single sentence? (Probably yes?)

Introductory considerations

If an email is expressly marked as confidential, e.g. in the email header or footer, it is obvious that it is itended as confidential (but it is not obvious that this alone makes the confidentiality legaly binding). The fact that some emails are expressly marked as confidential suggests that emails are not automatically considered confidential (but this is a mere suggestion; the fact that some people place a copyright notice on text does not mean that published text in a tangible form without that notice is not protected by copyright).

An email sent or received as part of employment is subject to a possible contractual requirement of confidentiality. Such an email does not even need to be marked as confidential to be prohibited from divulging outside of the employer organization (or outside of a broader scope, as specified in the employment contract).

A receiver of an email would seem advised to generally treat email content as confidential, by avoiding devulging the content (since it is not clear that it isn't confidential) and in case of a need to divulge, consult a lawyer?

The other way around, the sender has to consider the risk that the content will be divulged anyway. In this sense, sending an email is something of a pre-publication of a statement. It seems likely that a court can order divulging of the content of an email that was marked as confidential.

It is not clear whether the sender of the email holds copyright in its text; he would seem to if sending the email would be considered to be publishing. But sending an email does not really seem to be publishing proper.

Wiki context

Publishing content of emails sent via the wiki interface is dealt with in the further reading. As per Wikipedia:Emailing users#Reposting emails publicly:

"There is no formal consensus by the community regarding the act of reposting private off-wiki correspondence onto public Wikipedia locations, or the restriction or prohibition of the exercise thereof. However, it is often considered to be an unacceptable action for legal reasons. Unlike edits and posts to Wikipedia's web pages, emails that are sent through the email facility are not automatically "freely" licensed by the sender, and therefore, reposting the messages or correspondence to a public Wikipedia location would suggest or imply to any and all readers that the text is freely licensed for reuse and republication by its author, which is generally not the case.

"Users who feel that they are allowed to repost text from an email or other off-wiki source, or that doing so is necessary or the right to do so given a certain situation, discussion, report, or event, are advised to take extreme caution, and to consult with other trusted and experienced users before doing so, in order to ensure that the act will not accidentally create a problem for themselves, or create a negative perception or result in negative consequences. This might involve consulting, or asking the sender if they will allow the email to be quoted under Wikipedia's license in a post on Wikipedia's discussion pages. Note that this only applies to reposting on Wikipedia and its sister projects – other forms of quoting which do not involve risk of copyright breach (such as forwarding the text to an administrator for advice, or quoting words or brief phrases in a way that constitutes Fair Use) are generally unaffected by this concern."

In Wikipedia talk:Emailing users#email privacy, user Herostratus opined the following:

"[...] For one thing, the default rule in this world is that gentlemen don't publicize private correspondence without permission. (Exceptions might be made in some special rare cases, but in those cases its usually better to involve the authorities instead.) [...]"

It seems plausible enough (as for gentlemen), but is it accurate and how universal is it (what exceptions apply)?

Introductory considerations

Wiki context

Further reading