C.R.S. § 39-1-124
39-1-124. Mailing required to be sent by county assessor or treasurer - reasonable certain
39-1-124. Mailing required to be sent by county assessor or treasurer - reasonable certainty mailing will not be delivered. If a county assessor or treasurer has reasonable certainty that a mailing or notice required to be sent pursuant to this title 39 will not be delivered to a residential real property address by the United States postal service, the county assessor or treasurer is not required to send the mailing or notice to that residential real property address; except that this section does not apply to notices required to be sent pursuant to sections 39-11-128 and 39-10-111.5 (6)(b).