Is the Use of GMail an Ethics Violation?

What happens when a law firm uses an email service they know is not secure?  Does this constitute inadvertent disclosure?

"Client-Lawyer Relationship: Rule 1.6 Confidentiality Of Information

(c) A lawyer shall make reasonable efforts to prevent the inadvertent or unauthorized disclosure of, or unauthorized access to, information relating to the representation of a client."

Read the Article: Here