The Crime Prevention Research Center within the US Department of Justice outlined the folly of mass-mail ballots in their paper from August 2020.
“If concern about vote fraud with mail-in ballots is delusional, it is a delusion that is shared by most of the world. Even the countries that allow mail-in ballots have protections, such as government-issued photo-IDs. But Americans are constantly assured even this step is completely unnecessary. Without basic precautions, our elections are on course to become the laughing stock of the developed world.” –John R. Lott, Jr.
Download the document or view it as a PDF from the link above. The document is 141 pages divided into the following sections:
Main Findings, p. 2-6
Voting Rules for Developed OECD Countries, p. 7-9
Voting Rules for EU Countries, p. 10-11
Voting Rules for Other European Countries, p. 12-13
Detailed Voting Rules by Country, p. 14-141