Service Under RPAPL sec. 735
735. Manner of service; filing; when service complete
1. Service of the notice of petition and petition shall be made by personally delivering them to the respondent; or by delivering to and leaving personally with a person of suitable age and discretion who resides or is employed at the property sought to be recovered, a copy of the notice of petition and petition, if upon reasonable application admittance can be obtained and such person found who will receive it; or if admittance cannot be obtained and such person found, by affixing a copy of the notice and petition upon a conspicuous part of the property sought to be recovered or placing a copy under the entrance door of such premises; and in addition, within one day after such delivering to such suitable person or such affixing or placement, by mailing to the respondent both by registered or certified mail and by regular first class mail,
(a) if a natural person, as follows: at the property sought to be recovered, and if such property is not the place of residence of such person and if the petitioner shall have written information of the residence address of such person, at the last residence address as to which the petitioner has such information, or if the petitioner shall have no such information, but shall have written information of the place of business or employment of such person, to the last business or employment address as to which the petitioner has such information; and
(b) if a corporation, joint-stock or other unincorporated association, as follows: at the property sought to be recovered, and if the principal office or principal place of business of such corporation, joint stock or other unincorporated association is not located on the property sought to be recovered, and if the petitioner shall have written information of the principal office or principal place of business within the state, at the last place as to which petitioner has such information, or if the petitioner shall have no such information but shall have written information of any office or place of business within the state, to any such place as to which the petitioner has such information. Allegations as to such information as may affect the mailing address shall be set forth either in the petition, or in a separate affidavit and filed as part of the proof of service.
2. The notice of petition, or order to show cause, and petition together with proof of service thereof shall be filed with the court or clerk thereof within three days after;
(a) personal delivery to respondent, when service has been made by that means, and such service shall be complete immediately upon such personal delivery; or
(b) mailing to respondent, when service is made by the alternatives above provided, and such service shall be complete upon the filing of proof of service.