Why will my attachments not open in e-mails that are sent to me?

Is it illegal to open attachments in emails sent to you accidentally?

• I know legality depends on where you live, but I was hoping if I could get at least an idea of what most countries (US/EU) tend to think. I saw a similar topic here: http://security.stackexchange.com/questions/4206/is-it-illegal-to-read-an-e-mail-that-was-accidentally-sent-to-you but that revolved around reading an email, not opening/downloading an email attachment. For context, I've received a few emails lately from someone I've never met before but who is sending financial documents to me. While my first instinct was a phishing attempt, over the course of a week the emails have appeared more and more legitimate, including sending me passwords for site logins, documents being sent from banks (originating from the correct source, mind you), etc. Now I have not replied back to this person because I still believe it to be some sort of phishing/hijacking attempt, but I can't help but wonder what the attachments contain. This got me to wondering -- if I open the attachments to see what's inside, and they are legitimate, did the act of opening the attachment violate some sort of privacy law, especially if they relate to confidential matters (financial documents, etc)? I know the best solution would be to talk to a lawyer, but since the question was more a curiosity than a pressing legal question, I figured some people might know some resources I could at least look at, or some cases from the past regarding the issue.

• Answer:

  In my opinion (and sidestepping any discussion of what "illegal" means), the general answer to your question (in the US) is "no". I see no significant difference between information in an email and information in an attachment. A sender cannot impose contractual obligations on you without your consent. The general rule may not necessarily apply to lawyers, however. In particular (though there are many variations on this theme), a lawyer who receives information that is inadvertently disclosed by an opposing party must, at the least, so notify the disclosing party. Beyond that, requirements may not be entirely clear and may vary from state to state. Please see "You saw what?    Inadvertent disclosure and the attorney-client privilege" (http://apps.calbar.ca.gov/mcleselfstudy/mcle_home.aspx?testID=52) and "Respecting Someone Else's Confidential Information" (http://www.bryancave.com/files/Uploads/Documents/Respecting%20Someone%20Else%27s%20Confidential%20Information.pdf - New York).This answer is not a substitute for professional legal advice....