A few months ago, I wrote a blog post about 7 Tips for Subject Line Success. Since then, I’ve had a few different clients ask me my opinion about the use of symbols and other special characters in subject lines. My first response is almost always that you have to test it with your specific audience. More and more often, I see businesses using symbols in subject lines to help draw attention to individual emails in a cluttered inbox. But, is it working? Experian has....