I think this tool could interest some of you : http://www.subjectlinegold.com/ What is Touchstone? The only subject line tool that predicts the results of your email campaigns before you hit send. How does it work? Touchstone uses a proprietary algorithm to instantly predict the open, click and bounce rates of a given subject line by studying the past performance of similar lines. Are the results reliable? Using an online panel, we compiled a database of open rates for the 250 largest US senders. Then, using Touchstone, we were able to predict open rate performance to within 1-2% of the actual open rates.