Republican frontrunner Donald Trump's email list has less than half a million names, much less than Ben Carson (4.5 million), Ted Cruz (3.6 million), and Marco Rubio (2.4 million), according to eDataSource. While his list is small, Trump has the best deliverability across candidates with an average of 95.3 percent, just ahead of Chris Christe who touts a 92.9 percent deliverability rate.