The Lawyerist has revived the dialog on the ethics of lawyers using free email services like Gmail. It's good to see this debate continue, and I'll state up-front that the Lawyerist disagrees with my opinion on the subject. I still hold the position that a lawyer using an e-mail system that includes granting "a perpetual, irrevocable, worldwide, royalty-free, and non-exclusive licence" of the e-mail content to a third party is a problem. One of the Geeks recently shared this language with ethics counsel who laughed out-loud. His response was essentially that any lawyer who uses e-mail under this arrangement is crossing the line.
I realize bars and courts are still treating e-mail like it's mail. To demonstrate this thinking I suggest you ask them the ethics question a bit differently. I like to turn these questions around and direct them at a paper process to see how they sound. In this case: Would it be OK to grant FedEx an irrevocable license to the content in all of a lawyer's documents and letters it transports? I'm guessing you will get a different answer since Rule 1.6 is pretty clear on this issue: A lawyer shall not reveal information relating to the representation of a client unless the client gives informed consent. FedEx agreeing not to show this content to other people would be irrelevant, since the act of 'revealing' has already occurred.
I'll reiterate my prior advice to lawyers (and the Bar): if you want to hold yourself out as a profession with higher duties of care - then act like one.