https://www.vote.org/voter-id-laws/
Voter ID laws for mail in ballots by state.
Voter ID laws only started in 2006 or 2007 in one state. They've had no measurable effect on voter fraud because fraud is so low it's basically nonexistent compared to the overall vote:
Justin Levitt, a voting expert at Loyola Law School in Los Angeles, said voter fraud is rare but a stray case is not uncommon in elections. "You get a misguided family member once in a blue moon doing something they shouldn't be doing, and most of the rest of the frenzied, wildly inflated claims of thousands of ballots evaporate," he said.
In an earlier study, Levitt found 31 credible allegations of fraud out of more than 1 billion ballots cast from 2000 through 2014.
https://news.yahoo.com/single-nevada...l?guccounter=2
This election is no different. Mail in ballots are subject to various checks that make them as safe as in person voting. Half a dozen states have run elections entirely by mail in vote for decades now if I remember correctly.