Using emotional triggers in the subject line helped drive greater open rates among Mother's Day emails sent in 2014 and 2015, according to a report from Yesmail Interactive and Persado. The companies looked at emails sent by 13 retailer in the two week period leading up to the holiday and found that those companies that added language that triggered emotions in the subject line, the open rate was 10.3 percent, 21.5 percent greater than the average 8.5 percent.