I don't believe the concept of "voting by mail" is at question. It's the method of getting the ballots into individuals' hands. Sounds like you're referring to absentee ballots where someone registers in advanced for an absentee ballot and has it sent to them. _I believe_, in this case, vote by mail ballots are sent to currently registered voters by default. That means there are a flood of official ballots, meant for an individual, that are sitting in mailboxes, being sent to deceased people or people that have moved districts, etc. Those ballots can be filled in by someone else and can be intercepted to prevent counting.

That's how I understand the situation to be.