And it is not safe for a variety of reasons. It's not that we've suddenly discovered that the US mails are not working right.
But this has happened to a system that used to accommodate voters who couldn't get to the polls because of infirmity or age and requested a ballot. But now...
1. Election officials are mailing out ballots to almost everyone, often people who've died or moved. The election rolls are not cleared of registered voters who no longer are eligible to vote for years and years.
2. Mail-in ballots are not being checked to see if the signature on the envelope matches the one on file with the county clerk. To do that is a pretty mild form of verification, but now in some places it's being waived.
3. Depending on the state, ballots can be returned anywhere from a month before election day to a week or so AFTER the election.
4. Instead of returning one's ballot by mail, you can put it in a drop box, such as the one outside the door of the election clerk's office. So if getting to that voting precinct is too demanding for you, you can get all the way there except for going into the building. (?) These boxes are unguarded.
5. Mail-in ballots, often many of them, can be collected by a person who is not an authorized election worker and brought back by such people to the polls for counting. Such a person, not necessarily a relative or friend of the voter, might have gotten a ballot from some address where the voter no longer lives, or rounded up a bunch in a nursing home by saying they'll help those voters, or it may be that one family member decides to vote the ballot of his spouse or kids as well as his own. Recently a person who was a ballot harvester revealed that he'd been paid a certain sum, by an outside source, for each vote he rounded up. He claimed to have made tens of thousands of dollars that way.
To this situation, which accounts for thousands and thousands of votes, one political party says it's all for the convenience of the voter and that anyone who disagrees is in favor of "voter suppression." It's not voter suppression except in the sense of keeping invalid votes from being counted!