N.Y. Comp. Codes R. & Regs. tit. 7, § 721.2 – Definition.

(a) Privileged correspondence is defined as correspondence addressed by an inmate to any of the following persons or entities at their official business address, or, except as noted in subdivision (b) of this section, received from such persons or entities:
1. (1) Governmental/public officials. Any American Federal, state, or local government official, department or agency; any official of a nation, state, or tribe of which the inmate is a citizen; or the correctional association of New York State;
2. (2) Legal services. Any attorney, approved legal representative, representative employed or supervised by an attorney, or any legal services organization; or
3. (3) Medical services. Medical personnel such as physicians and dentists; or hospitals.
(b) The following shall not be defined as privileged correspondence but shall be processed as general incoming correspondence in accordance with Part 720 of this Title, "Inmate Correspondence Program":
1. (1) mail which is not delivered in an envelope bearing the identity and official business return address of one of the above listed persons or entities;
2. (2) mail received from a board of elections;
3. (3) mail received from the Department of Motor Vehicles;
4. (4) mail received from the State Education Department, excluding materials sent to inmates marked "legal mail" by the New York State Library's Prisoner Services Project;
5. (5) mail received from any county or local tax assessor or clerk, except for a clerk of a court (note: notwithstanding that a county clerk may also be a clerk of a court, mail from a county clerk shall be processed as general incoming correspondence); and
6. (6) mail received from the Secretary of State, Department of State, corporation division or uniform commercial code unit of any state.
(c) This regulation does not, in itself, establish a confidential relationship between the sender and recipient of correspondence identified herein as privileged (e.g., a central office official in receipt of privileged mail may share that mail, and any response to it, as deemed appropriate). The privileges which apply to correspondence defined in this section relate to processing controls, allowances of limited free postage and advances of inmate funds for postage. These privileges are detailed in section 721.3 of this Part.