Sec. 1.5. (a) As soon as letters testamentary or letters of administration have been issued, the clerk of the court shall serve by mail notice of the petition on each of the decedent's heirs at law, if the decedent died intestate, or the devisees and legatees under the decedent's will. The mailing of notice under this subsection may not be waived.
(b) The notice required under subsection (a) shall read substantially as follows: