The phrase "Free delivery" is an effective one for an email subject line, as emails that use this have a 50.7% higher open rate and a 135.4% click through rate compared to other emails, according to a new study by marketing services company Adestra. The report also revealed that emails that have the word "alert" in their subject lines have a 38.1% higher than average open rate and a 61.8% higher click through rate. Some words tip the scales in the opposite direction. Using the word "report" lowers the open rate to 23.7% below average and click through rates drop 54.8%. The word "learn" also had an adverse effect on open and click through rates, averaging -35.5% and -60.8% respectively.