ORS § 223.391
If a notice is required to be sent to the owner of a lot affected by a proposed assessment, the notice shall be addressed to the owner or the owner's agent. If the address of the owner or of the owner's agent is unknown to the recorder, the recorder shall mail the notice addressed to the owner or the owner's agent at the address where the property is located. Any mistake, error, omission or failure with respect to the mailing shall not be jurisdictional or invalidate the assessment proceedings, but there shall be no foreclosure or legal action to collect until notice has been given by personal service upon the property owner, or, if personal service cannot be had, then by publication once a week for two successive weeks in a newspaper designated by the governing body and having general circulation within the boundaries of the local government where the property is located.
ORS 223.391