Section 19. A landlord or lessor of any real estate except an owner-occupied two- or three-family dwelling shall, within a reasonable time following receipt of a written notice from a tenant forwarded by registered or certified mail of an unsafe condition, not caused by the tenant, his invitee, or any one occupying through or under the tenant, exercise reasonable care to correct the unsafe condition described in said notice except that such notice need not be given for unsafe conditions in that portion of the premises not under control of the tenant. The tenant or any person rightfully on said premises injured as a result of the failure to correct said unsafe condition within a reasonable time shall have a right of action in tort against the landlord or lessor for damages. Any waiver of this provision in any lease or other rental agreement for residential use shall be void and unenforceable. The notice requirement of this section shall be satisfied by a notice from a board of health or other code enforcement agency to a landlord or lessor of residential premises not exempted by the provisions of this section of a violation of the state sanitary code or other applicable by-laws, ordinances, rules or regulations.