R.I. Gen. Laws § 23-27.3-122.1.2: Notice or orders — Service and content.

Every notice or order authorized by this code shall be in writing and shall be served on the owner or the person responsible as defined in Article 2:

(1) By any person authorized to serve civil process within the state, by serving a copy of the order or notice personally upon the owner or person responsible or by leaving a copy of the order or notice at the owner or person responsible’s last and usual place of abode; or

(2) By sending the owner or person responsible a copy of the order or notice by regular mail and certified mail, to the last known address of the owner or owners; or

(3) If the last and usual place of abode of the owner or person responsible is unknown, and a due and diligent search fails to locate the individual, by posting a copy of the order or notice in a conspicuous place on or about the premises in violation.