The question is, can they guarantee a 100% accurate vote count. The answer is no.

There are too many possible problems with mail-in.

First is the person on the ballot, the person filling out the ballot. There is no proof of I.D. Will all the signatures match the one on record? Is the person still alive?

An example, there are many houses that will receive several ballots. Will one of these persons fill out all of the ballots? Is there 100% guarantee the post office will deliver 100% of the ballot in time to be counted?

Will the people counting the votes be 100% accurate? These are just a few ways to cheat. There are more. When there are this many ways to cheat, then there is a 100% guarantee it will happen. We may not know who wins the election for weeks after the election.

They give the reason for mail-in is the virus. That is just an excuse to cheat. What should be done to make it safe at the polls is to extend the number of days to vote. This way the polls would not be crowded.