(a) In representing a client, an attorney shall not use means that have no substantial purpose other than to embarrass, delay, or burden a third person, or use methods of obtaining evidence that violate the legal rights of such a person.

(b) An attorney who receives a document, electronically stored information, or other property relating to the representation of the attorney's client and knows or reasonably should know that the document, electronically stored information, or other property was inadvertently sent shall promptly notify the sender.

[1] Responsibility to a client requires an attorney to subordinate the interests of others to those of the client, but that responsibility does not imply that an attorney may disregard the rights of third persons. It is impractical to catalogue all such rights, but they include legal restrictions on methods of obtaining evidence from third persons and unwarranted intrusions into privileged relationships, such as the client-attorney relationship.

[2] Section (b) recognizes that attorneys sometimes receive a document, electronically stored information, or other property that was inadvertently sent or produced by opposing parties or their attorneys. A document, electronically stored information, or other property is inadvertently sent when it is accidentally transmitted, such as when an email or letter is misaddressed or a document, electronically stored information, or other property is accidentally included with information that was intentionally transmitted. If an attorney knows or reasonably should know that such a document, electronically stored information, or other property was sent inadvertently, this Rule requires the attorney promptly to notify the sender in order to permit that person to take protective measures. Whether the attorney is required to take additional steps, such as returning the document, electronically stored information, or other property, is a matter of law beyond the scope of these Rules, as is the question of whether the privileged status of a document, electronically stored information, or other property has been waived. Similarly, this Rule does not address the legal duties of an attorney who receives a document, electronically stored information, or other property that the attorney knows or reasonably should know may have been inappropriately obtained by the sending person. For purposes of this Rule, “document, electronically stored information, or other property” includes, in addition to paper documents, email and other forms of electronically stored information, including embedded data(commonly referred to as “metadata”), that is subject to being read or put into readable form. Metadata in electronic documents creates an obligation under this Rule only if the receiving attorney knows or reasonably should know that the metadata was inadvertently sent to the receiving attorney.

[3] Some attorneys may choose to return a document or delete electronically stored information unread, for example, when the attorney learns before receiving it that it was inadvertently sent. Where an attorney is not required by applicable law to do so, the decision to voluntarily return such a document or delete electronically stored information is a matter of professional judgment ordinarily reserved to the attorney. See Rules 19-301.2 and 19-301.4.

Model Rules Comparison-- Rule 19-304.4 is substantially similar to the language of Model Rule 4.4 of the Ethics 2000 amendments to the ABA Model Rules of Professional Conduct.