In In re Actos Antitrust Litigation, No. 1:13-cv-09244 (RA) (SDA), — F.R.D. —-, 2022 WL 949798 (S.D.N.Y. March 30, 2022), Defendant produced responsive emails using “threading,” to reduce volume. Plaintiff, however, had never agreed to the use of threading, and the parties’ electronically stored information (ESI) protocol was silent about utilizing threading. And so, Plaintiff filed a motion seeking to compel production of “earlier-in-time” emails that were produced as part of “threaded” emails. Ultimately, the court concluded that the use of threading was not appropriate where, as here, the parties had not agreed to its use. The court also provided helpful guidance about how to log for privilege purposes, emails that had been threaded.

Email Threading and ESI Protocols

Many of you reading this may be asking, “what in the world is threading?” Simply put, email threading is the identification of email relationships (i.e., threads, people involved in a conversation, and duplicate emails) and groups them together so you review the most comprehensive single email discussion. Then, typically, you produce only the most inclusive email thread, rather than each of the earlier-in-time emails reflected in the comprehensive email.[1] This review strategy minimizes the number of documents one has to review and also reduces the total volume of emails produced.

Here, the parties entered a protocol for the production of ESI in native file format that required, among other things, the parties to de-duplicate the ESI produced. The protocol did not, however, address the use of email threading, which one of the defendants used without plaintiffs’ knowledge or consent. Id. at *1. And, while Plaintiff received the earlier in time emails as part of the production, plaintiffs wanted the “earlier-in-time emails” as well as the metadata associated with those emails.

Magistrate Judge Aaron began by noting the importance of a comprehensive ESI protocol. Id. at *2. Relying upon the Sedona Principles he noted “early discussions” regarding “procedural issues relating to the form of production” is critical and parties should enter into an “agreed upon protocol governing the production of ESI [to] avoid downstream misunderstandings or disputes.” Id. (quoting The Sedona Principles, Third Edition: Best Practices, Recommendations & Principles for Addressing Electronic Document Production, 19 Sedona Conf. J. 1, Comment 3.c. (2018)).

Ultimately, Magistrate Judge Aaron declined to impose email threading on Plaintiffs. Even though he recognized that the use of threading can be a valuable tool and the production of earlier in time emails would cause some additional burden on Defendant, he found any such additional burden was not undue as Defendant agreed to the ESI protocol that was silent on the use of threading.[2]

How to Log Threaded Emails

Magistrate Judge Aaron also provided guidance regarding how email threads should be identified on privilege logs. He noted that Local Civil Rule 26.2(c) provides that “when asserting privilege on the same basis with respect to multiple documents, it is presumptively proper to provide the information required by this rule by group or category.” Id. at *4. Magistrate Judge Aaron also quoted the committee note to this local rule, that “[b]ecause the appropriate approach may differ depending on the size of the case, the volume of privileged documents, the use of electronic search techniques, and other factors, the purpose of Local Civil Rule 26.2(c) is to encourage the parties to explore methods appropriate to each case.” Based on these principles, Magistrate Judge Aaron concluded that categorical privilege logs are appropriate and adequate “if [the log] provides information about the nature of the withheld documents sufficient to enable the receiving party to make an intelligent determination about the validity of the assertion of the privilege.” And so, it is important to give thought to privilege logs and what will be acceptable when drafting a protocol. Indeed, this case serves as an important reminder that many ESI disputes can be avoided by a well negotiated and comprehensive ESI protocol.


[1] For example, I sent an email to my colleague Jim Smith at 9:00 am. Jim responds at 9:15. I then reply at 9:30. With email threading, these three emails would be grouped together with only the most comprehensive email (i.e., the 9:30 communication) reviewed and produced. The idea being the two earlier emails are reflected within the larger chain, and duplicative. If a side discussion occurred (i.e., Jim forwards my 9:00 am email to Barbara), that email would be separately captured and reviewed.

[2] The court also observed that Defendant’s exclusion from production of lesser included emails resulted in a number of issues such as the exclusion of the metadata associated with those earlier emails, which compromised Plaintiffs’ ability to search for all correspondence within a date range. In this regard, Magistrate Judge Aaron noted that the parties could have included in the ESI protocol provisions for the production of metadata to resolve such issues, but Plaintiffs were not provided the opportunity to negotiate how email threading might be accomplished in an acceptable manner. This serves as an important reminder that one must spend time drafting and negotiating a proper ESI protocol.

Photo of Kathryn C. Cole Kathryn C. Cole

Kathryn C. Cole represents large and small businesses, financial institutions, and individuals in virtually all aspects of federal and state court commercial litigation, arbitration and mediation, and before federal agencies and regulatory bodies. In addition to advising on electronic data and cyber-related issues…

Kathryn C. Cole represents large and small businesses, financial institutions, and individuals in virtually all aspects of federal and state court commercial litigation, arbitration and mediation, and before federal agencies and regulatory bodies. In addition to advising on electronic data and cyber-related issues, Katy has considerable experience in all areas of complex litigation including contract claims, product liability claims, tort claims, consumer class-action claims and securities class-action claims.