Md. Code, Election Law § 9–504

(a) A voter may return a vote–by–mail ballot to a local board:

(1) by mail;

(2) in person during regular office hours;

(3) through a ballot drop box; or

(4) through a duly authorized agent in accordance with subsection (b) of this section.

(b) (1) A voter may designate a duly authorized agent in accordance with § 9–307 of this title to return a vote–by–mail ballot to a local board during regular office hours.

(2) Notwithstanding § 9–307(b)(4)(i) of this title, an agent is required only to:

(i) witness the voter mark the ballot and place it in an envelope; and

(ii) return the ballot to a local board.