Maryland Code, Family Law § 5-3A-15

(1) personal service; or

(2) certified mail, restricted delivery, return receipt requested.

(d)(1) If a court is satisfied, by affidavit or testimony, that, after reasonable efforts in good faith, a petitioner could not identify a parent or could not effect service on a parent, the court shall order service through notice by publication as to that parent.

(2) Notice under this subsection shall consist of substantially the following statement:

To: (Father's name)

To: (Mother's name)

To: Unknown parent

“You are hereby notified that a guardianship case has been filed in the circuit court for (county name), case no. (number). All persons who believe themselves to be parents of a (male or female) child born on (date of birth) in (city, state) to (mother's and father's names and dates of birth) shall file a written response. A copy of the show-cause order may be obtained from the clerk's office at (address) and (telephone number). If you do not file a written objection by (deadline), you will have agreed to the permanent loss of your parental rights to this child.”

(3) Service under this subsection shall be by:

(4) The Department may charge a petitioner a reasonable fee to cover the cost of posting.