Marketing service provider Worldata launched SubjectLine.com to help email marketers get the best results from their campaigns. The Subject Line Scoring Tool enables Web pros to test subject lines for deliverability issues and receive marketing-related suggestions for improving open rates.
The tool is free, but users must fill out a registration form to continue using it after the initial trial. The subject line ratings are based on more than a billion email messages that have been sent and tracked via partners and clients of SubjectLine.com.
More than 400 rules are tested, from evaluating filtering and deliverability issues to marketing and performance-related concerns. During a brief trial of my own, I entered what I considered to be one good subject line and one bad one.
In my opinion, both were rated pretty accurately. Both tests came back with a list of reasons for the scores they received, including deliverability and marketing issues (see below).