I read the Snopes article and it said that Jewing's Tea Party chain mail is bullshit.
"Even if these numbers are assumed to be accurate, presenting them as definitively demonstrating that “some 3.5 million more people are registered to vote in the U.S. than are alive among America’s adult citizens” is a questionable and problematic claim, given that the information was compiled from only 462 counties in 38 states, yet the entire U.S. comprises over 3,000 counties in fifty states. Many of those other counties might well have substantially fewer registered voters on their rolls than adult residents who are eligible to vote.
Another major issue with such a claim is the potential inclusion of “inactive” voters among the tallies of registered voters, a matter that was publicized in a 1 August 2017 letter Judicial Watch sent to California Secretary of State Alex Padilla threatening to sue unless the state and eleven of its counties produced voter records to them. According to Judicial Watch, their own analysis of U.S. Census data and voter registration records indicated those eleven counties included numbers of registered voters exceeding the numbers of adults eligible to vote in those counties."