This difference means that while all communications between a lawyer and his/her client are confidential, not all communications are privileged such that they would be protected from disclosure in a lawsuit.
So if confidential, non-privileged information can be compelled for disclosure, then how can it be termed "confidential"? 'Confidentiality' feels like a too forceful misnomer.
Details. Optional Reading.
p. 39 Bottom
2) E-mail Disclaimers
Nerd alert: I love assessing the e-mail disclaimers that individual lawyers and law firms use, especially as they relate to matters priv-ileged and confidential.
The laziest of these notices merely assert that the content of the e-mail is privileged and confidential. But wait, you're my lawyer
friend and you've just asked me by e-mail if I'm free for a beer on Friday. That's privileged and confidential? Of course it isn't. In most cases, this isn't an issue, but on a big litigation file you might find yourself struggling before a judge to say why something con. tentious is privileged and confidential when it becomes apparent that you routinely slap the disclaimer on everything you send, drink invitations included.
A bit more thoughtful is the disclaimer that the contents of the e-mail may be privileged and confidential. But only a bit; you've admitted that not everything a lawyer sends will be privileged or confidential, but it still looks like you haven't thought about whether the actual communication is or not. This isn't better than saying everything's privileged and confidential, if push comes to shove.
It is preferable to have no boilerplate disclaimer at all, and to label something as privileged and confidential when it truly is, in the subject line of the e-mail and at the top of the underlying message, as well as in the fine print underneath. Putting this into practice would be a nuisance, however —and would require some thought.
And you must think about whether what you send is privileged at all: I think it drove a former general counsel boss of mine crazy when I identified information as confidential only, but I was cor-rect as a matter of law; only actual legal advice is privileged, not facts or even suggestions for your readers to consider legal issues and reach their own conclusions.
Ashurst explains that confidentiality is a necessary, but not sufficient, condition for privilege:
However, while confidentiality is an essential ingredient of a privileged communication, just because a document is confidential does not necessarily mean it is also privileged.
Herbert Smith Freehills presents a helpful decision tree on p. 2 of the PDF: