Experian also notes that employing newish symbols requires testing. "If you test using symbols in your subject lines and see great results at first that taper off, perhaps the 'newness' has worn off. Try testing new symbols or testing symbols against no symbols."
Of course, some symbols appear as themselves in certain email clients while others become gobblygook, which is a big turn-off to prospects. Make sure you test your favorite new symbols in different email clients and on different devices to make sure your thumbs up doesn't end up a big thumbs down in open rate!
Ethan Boldt is the chief content officer of Direct Marketing IQ, the home of direct marketing research and Who's Mailing What!, the most complete library of direct mail and email in the world. To watch a quick video about Who's Mailing What!, go to www.whosmailingwhat.com/video. He can be reached at firstname.lastname@example.org.