All-mail voting is of course the most conducive to fraud since the counting can be done in total secrecy.
Secrecy = what? Counting by election officials? How is that any different than how they count all paper ballots?
At least in Massachusetts, the voter puts his/her own vote in the ballot box, in full view of the (volunteer) election officials, who then count the ballots immediately after voting ends. It's very difficult to have counting fraud unless all the volunteer election officials are in on it (which is not unheard of, certain Boston precincts occasionally break 100% turnout). You essentially have to take their word for it much more in an all-postal situation.
