There is nothing that invites fraud more than vote by mail.  It would be better to eliminate all vote by mail than it would be to implement voter ID.  Though that is a false choice, as steps can be taken to increase security in both places, the fact remains that voting outside of a precinct is the most fertile territory for fraud to occur, as it may have in Rhode Island:

“We have already written here of questions raised in North Smithfield, where a winning General Assembly candidate captured the mail ballot vote by wide margins in five precincts but lost in a sixth, where a nursing home requested 50 mail ballots. More recently, similar questions have been raised about results in several South Providence precincts, where mail ballot votes in the Providence mayor’s race seemed to run contrary to the overall election results.”