Trump Tweeted a 2012 NYT article spelling out the perils of absentee ballots.
The gist of it is that the ballots lend themselves to fraud and corruption.
The big issue is verification.

https://www.nytimes.com/2012/10/07/...ulty-ballots-could-impact-elections.html

Nothing has changed except that the NYT hates Trump....so this article has become an inconvenient truth

Excerpts from article

There is a bipartisan consensus that voting by mail, whatever its impact, is more easily abused than other forms. In a 2005 report signed by President Jimmy Carter and James A. Baker III, who served as secretary of state under the first President George Bush, the Commission on Federal Election Reform concluded, “Absentee ballots remain the largest source of potential voter fraud.”

"In 2008, Minnesota officials rejected 12,000 absentee ballots, about 4 percent of all such votes, for the myriad reasons that make voting by mail far less reliable than voting in person."


https://soundcloud.com/sunset-poet-of-texas