In Gaskins v. Unemployment Compensation Bd. of Review, 59 Pa. Commw. 213, 429 A.2d 138, 140 (Pa. Cmwlth. 1981), the Court held: If there is evidence in the record that the determination of the Bureau was mailed to the claimant's last known address, and that the notice was not returned to the Bureau by the postal officials as undeliverable, then there is a presumption of the regularity of administrative acts of public officials which the referee may invoke in reaching a determination that the claimant did have proper notice.