From Multiquip Inc. v. Water Mgmt. Sys. LLC, 2009 U.S. Dist. LEXIS 109148 (D. Idaho Nov. 23, 2009):

On March 31, 2009, Defendants' counsel, Rick Klingbeil, wrote an email to his client, Defendant David Muhs.... On April 8, 2009, Mr. Muhs responded to Mr. Klingbeil via email, also directing his correspondence (with the underlying March 31, 2009 email attached) to Roy Thompson and Matteo Tagliani.... Like Mr. Klingbeil, Mr. Thompson represents Mr. Muhs in this action; Mr. Tagliani, however, does not. According to Defendants, the "autofill" feature on Mr. Muhs' email program inadvertently supplied Mr. Tagliani's name instead of the intended recipient, Mr. Mark Hubert — a third attorney representing Mr. Muhs here. ***

The analysis under FRE 502(b)(1) essentially asks whether the party intended a privileged document to be produced or whether the production was a mistake. Compare FRE 502(a)(1) (discussing waiver that is "intentional" in contrast to FRE 502(b)(1)'s requirement for waiver to be "inadvertent"). Mr. Muhs' Declaration ... unequivocally establishes that his email to Mr. Tagliani was inadvertent.... Moreover, it does not stretch the boundaries of one's imagination to see how such a situation can happen. As one commentator noted:

Because of recent advancements in communication technology, more documents are exchanged today than ever before. This recent proliferation of both electronic communications and electronic documents has dramatically increased the frequency with which mistakes can happen. Consequently, it is easier to make a mistake. Now it only takes the click of a mouse — an accidental "reply to all," for example — to inadvertently transmit a privileged electronic file.

8 N.C.J.L. & Tech. 231, 233 (Spring 2007). Mr. Muhs made a mistake — a potentially costly mistake in that, regardless of whether Defendants' Motion is granted, the "cat is out of the bag" with respect to Plaintiff's counsel's awareness of Defendants' original strategy for contacting Mr. Parma. Whether such knowledge affects the parties' interactions moving forward remains to be seen. Still, for the purposes of FRE 502(b), there is no real dispute that Mr. Muhs did not intend to forward along his privileged correspondence between him and his counsel to a third party. The Court therefore finds that Mr. Muhs' April 8, 2009 email to, among others, Mr. Tagliani, was not intended and, thus, inadvertent.

[Footnote 4] Plaintiff acknowledges that Mr. Muhs mis-sent his email to Mr. Tagliani, however argues that doing so outside a discovery context amounts to a waiver....The Court is not convinced that any protections accompanying a party's inadvertent disclosure apply only when made during discovery. See Fed. R. Evid. 502 Advisory Committee Notes ("[This Rule] responds to the widespread complaint that litigation costs necessary to protect against waiver of attorney-client privilege or work product have become prohibitive due to the concern that any disclosure (however innocent or minimal) will operate as a subject matter waiver of all protected communications or information." (Emphasis added)). First, Plaintiff offers no authority limiting such an application. Second, and more fundamentally, the Court sees no legitimate reason for limiting the attorney-client privilege's protections to discovery situations. Either the privilege applies or it does not; likewise, the privilege is either waived or it is not. Whether this takes place within a discovery context is immaterial toward maintaining the privilege under FRE 502(b).

***

Instead, it must be recognized that an email program's autofill function operates as both a blessing and curse — saving users time when addressing email correspondence, yet risking the potential for sending that correspondence to an unintended recipient. Here, consistent with his standard of practice with respect to corresponding with his counsel via email, Mr. Muhs utilized his email program's autofill feature to list his communication's addressees. ***

Mr. Muhs' care in addressing his email was hasty and imperfect. Nevertheless, "he relied on a system that had worked in a particular way in the past to continue working the same way in the future." *** Under these circumstances, it cannot be said that Mr. Muhs' isolated act was unreasonable. Therefore, the Court finds that Mr. Muhs took reasonable steps to prevent the disclosure.