N.Y.C. Admin. Code § 11-417: § 11-417 Mailing notices to other interested persons.

The commissioner of finance shall mail a notice of foreclosure and any other process required by this chapter to each person who is not entitled to have tax bills mailed to such person by the commissioner of finance, but who has notified the commissioner of finance in writing or electronically that he or she has an interest in real property, including the interest of a mortgagee, lienor or encumbrancer, and who has requested the commissioner of finance to mail a notice to him or her at a designated mailing address, at the address so provided, whenever the property in which the person has an interest is included in a list of delinquent taxes filed pursuant to this chapter. However, failure to receive such notice or process shall not affect the validity of any proceeding brought pursuant to this chapter.