Please elaborate on how the fraud would work in this case...
The DA dropped the case, but they also know where their bread is buttered.
https://www.sfgate.com/politics/article/Allegations-of-voter...
Some mail in ballots have party identification on them, so you can ignore envelopes from the opposing party.
Identification is based on signature matching (that your signature matches the one when you registered). According to the ACLU thousands of mail-in ballots get thrown out in California just because of a perceived signature mismatch.
https://www.courthousenews.com/california-trashes-thousands-...
You can mail in a ballot and then go vote in person on Election Day, or have another ballot "harvested" from you by a canvaser.
Anyone (spouse, significant other, parent) could take your ballot, fill it out, sign it, and mail it in.
Human beings are terrible, and the idea that somehow that a partisan board of elections would be above this stuff is laughable. Everything in politics is corrupt, the corruption isn't suspended on Election Day.
People should only be allowed to vote in-person with an ID, unless they have a disability that otherwise prevents them from doing so.
Many of these are a problem with in-person voting as well. None of us actually see our ballots getting added to the global total, so in theory somebody could just throw out the votes they don't like. Somebody could easily impersonate voters. Somebody could go vote in multiple places. Somebody could just threaten people with a gun and say they'll shoot them if they don't vote the right way.
But in practice these are not a big problem. That's partly because election officials and election nerds are not dummies. And it's partly because that all is illegal, and shifting vote totals enough to win an election with the safeguards in place is at best very difficult.
If you mail people blank ballots, on the day the ballots go out someone could follow the mail truck around the neighborhood stealing them all out of the mailboxes, both disenfranchising everyone in that neighborhood and providing the theives with blank ballots they could fill out and submit.
It opens you up to fresh chicanery like giving people "updates" on where to mail their ballots and having voters send them to the perpetrators who then either modify the ballots before submitting them or only submit the favorable ones.
It creates the possibility that somebody figures out how to forge ballots and then prints off as many as they like and mails them in, because there are no poll workers there to observe anything.
And then what do you do? Hold another election? What happens if they just do it again and hope nobody notices this time? Or do it again just to cause grief and delay the election results?