Because the attorney-client privilege focuses primarily on content rather than context, most courts do not find that the privilege protects non-substantive transmission communications such as e-mail headers. On the other hand, the work product doctrine focuses primarily on context rather than content ‑‑ so that separate protection often covers even non-substantive transmission communications.
In Schuler v. Invensys Building Systems, Inc., No. 07 C 50085, 2009 U.S. Dist. LEXIS 13067, at *5 (N.D. Ill. Feb. 20, 2009), the court applied both protections to defendant’s e-mail headers, “which contain information about the sender, recipients, time stamp, and subject line.” The court explained that this type of header “gives the opposing party three pieces of potentially valuable information to which it would not otherwise have access: the topic of discussion between certain people, the identities of those people, and a time at which the discussion took place.” Id. at *5-6. The court further explained that such information “could give an opposing party an advantage when making time sensitive decisions, or when building a time-line” in connection with any litigation. Id. at *6.
Most courts would take such a broad view in the work product context (although many litigants produce such headers if they do not seem harmful), but not in the privilege context.