Maryland Code, Estates and Trusts § 1-103

(b) A subsequent notice is sufficient if deposited as first-class mail, postage prepaid, addressed to the same address at which the first notice was received or, after notice in writing from the addressee of a change of address, to his new address.

(c) If no return receipt is received apparently signed by the addressee, and there is no proof of actual notice, no action taken in a proceeding may prejudice the rights of the person entitled to notice unless proof is made by verified writing to the satisfaction of the court or register that reasonable efforts to locate the addressee and warn him of the pendency of the action have been made.

(d) If the person to whom notice is sent is a minor or disabled person, and the minority or disability was not known to the sender at the time of the first notice, but was later discovered, any subsequent notice shall be sent to the judicially appointed guardian, if any, or, if none, the parent of the minor or disabled person, or other person who has assumed responsibility for the minor or disabled person.