Mass mail voting
In absentee voting, an actual registered voter must request an absentee ballot, and that registered voter can mark and return that ballot.
In mass mail voting, each state may have its own rules, but generally, the state tries to send a ballot to every resident. Some of these ballots will go to actual registered voters; some will go to registered voters who have died; some will go persons who have left the state; some will go to infants; a few will go to dogs and cats.
Almost all of these mailed ballots will be opened by somebody, and whoever opens that ballot can mark it, and send it back.
I wish us good luck.
Ralph B Blasier