Chain of custody should always be a focus. And you cannot have that through the mail.
The idea that boxes of ballots are “found” in storage rooms or the trunks of cars is abhorrent. And it just gets much worse if we rely on the mailman to suddenly show up with more votes.
Postmark cancellations are critical to determine if the vote was cast prior to the close of polling. Absent postmarks, the votes cannot be legally counted.
Why couldn’t the ballot be sent by certified mail, where you had to show an ID?