NY CPLR § 2103 (2021)
2021 New York Laws CVP - Civil Practice Law and Rules Article 21 - Papers R2103 - Service of Papers.

Rule  2103.  Service  of  papers.  (a)  Who  can  serve.  Except where otherwise prescribed by law or order of court, papers may be  served  by any person not a party of the age of eighteen years or over.  (b)  Upon  an  attorney.  Except  where otherwise prescribed by law or order of court, papers to be served upon a party  in  a  pending  action shall  be  served  upon  the  party's  attorney. Where the same attorney appears for two or more parties, only one copy need be served  upon  the attorney.  Such service upon an attorney shall be made:   1. by delivering the paper to the attorney personally; or   2.  by  mailing the paper to the attorney at the address designated by that attorney for that  purpose  or,  if  none  is  designated,  at  the attorney's  last  known  address; service by mail shall be complete upon mailing; where a period of time prescribed by law is measured  from  the service  of  a paper and service is by mail, five days shall be added to the prescribed period if the mailing is made within the  state  and  six days  if  the  mailing  is  made  from  outside the state but within the geographic boundaries of the United States; or   3. if the attorney's office is open,  by  leaving  the  paper  with  a person  in  charge,  or  if  no  person is in charge, by leaving it in a conspicuous  place;  or  if  the  attorney's  office  is  not  open,  by depositing  the  paper,  enclosed  in  a  sealed wrapper directed to the attorney, in the attorney's office letter drop or box; or   4. by leaving it at the attorney's residence within the state  with  a person  of  suitable  age and discretion. Service upon an attorney shall not be made at the attorney's residence unless service at the attorney's office cannot be made; or   5.  by  transmitting  the  paper  to   the   attorney   by   facsimile transmission,  provided  that a facsimile telephone number is designated by the attorney for that  purpose.  Service  by  facsimile  transmission shall  be  complete  upon the receipt by the sender of a signal from the equipment of the attorney served indicating that  the  transmission  was received,  and  the mailing of a copy of the paper to that attorney. The designation of  a  facsimile  telephone  number  in  the  address  block subscribed  on  a  paper  served  or filed in the course of an action or proceeding shall constitute consent to service by facsimile transmission in accordance with this subdivision. An attorney may change or rescind a facsimile telephone number by serving a notice on the other parties; or   6. by dispatching the paper to  the  attorney  by  overnight  delivery service  at  the address designated by the attorney for that purpose or, if none is designated, at the attorney's last known address. Service  by overnight  delivery  service shall be complete upon deposit of the paper enclosed in a  properly  addressed  wrapper  into  the  custody  of  the overnight  delivery  service for overnight delivery, prior to the latest time  designated  by  the  overnight  delivery  service  for   overnight delivery.  Where a period of time prescribed by law is measured from the service of a paper and service is by overnight  delivery,  one  business day  shall  be  added  to  the  prescribed  period.  "Overnight delivery service" means any delivery service which regularly  accepts  items  for overnight delivery to any address in the state; or   7. by transmitting the paper to the attorney by electronic means where and in the manner authorized by the chief administrator of the courts by rule  and,  unless  such rule shall otherwise provide, such transmission shall be upon the party's written consent. The  subject  matter  heading for  each  paper  sent by electronic means must indicate that the matter being transmitted electronically is related to a court proceeding.  (c) Upon a party. If a party has not appeared by an  attorney  or  the party's  attorney cannot be served, service shall be upon the party by a  method specified in paragraph one, two, four, five or six of subdivision (b) of this rule.  (d)  Filing.  If  a  paper  cannot  be  served  by  any of the methods specified in subdivisions (b) and (c), service may be made by filing the paper as if it were a paper required to be filed.  (e) Parties to be served. Each paper served  on  any  party  shall  be served on every other party who has appeared, except as otherwise may be provided by court order or as provided in section 3012 or in subdivision (f)  of section 3215. Upon demand by a party, the plaintiff shall supply that party with a list of those who have  appeared  and  the  names  and addresses of their attorneys.  (f) Definitions. For the purposes of this rule:   1.  "Mailing"  means  the deposit of a paper enclosed in a first class postpaid wrapper, addressed to the address designated by  a  person  for that  purpose  or,  if  none  is designated, at that person's last known address, in a post office or official  depository  under  the  exclusive care  and  custody of the United States Postal Service within the United States;   2. "Electronic means" means any method of transmission of  information between  computers or other machines designed for the purpose of sending and receiving such transmissions, and  which  allows  the  recipient  to reproduce   the   information   transmitted  in  a  tangible  medium  of expression;   3. "Facsimile  transmission"  means  any  method  of  transmission  of documents  to  a  facsimile  machine  at  a  remote  location  which can automatically produce a tangible copy of such documents.