N.Y. Est. Powers & Trusts Law § 11-1.4

§ 11-1.4 Validity of execution of power to sell, mortgage or lease real\n property by less than all qualifying executors\n Any deed, mortgage or lease duly executed by one or more, but not all,\nof the executors or trustees who qualified conveys the full title and\ninterest of the testator, and is as effective as if all the executors or\ntrustees who qualified had joined in the execution thereof, when ten\nyears have elapsed since the recording of such deed, mortgage or lease\nin the county where the property affected is situated; saving, however,\nthe rights of every grantee, mortgagee or lessee, in good faith and for\na valuable consideration, deriving title under an instrument executed by\nall the executors or trustees who qualified to the same property or any\npart thereof, whose deed, mortgage or lease is duly recorded before such\nperiod of ten years has elapsed.\n