Litmus recommends around 50 characters. Yes Lifecycle Marketing says emails with subject line up to 20 characters have ethe highest average open rate, unique click rate, and click-to-open rate. An analysis from Retention Science found that subject lines with 6 to 10 words results in the highest open rates. And Return Path advises using 61 to 70 characters.
Now, you can automatically send highly relevant emails encouraging them to buy the product or service they were considering. Customers who received multiple abandoned shopping cart emails are 2.4 times more likely to complete the purchase than those who receive only one followup email, according to Experian. Try sending the first message one day after, a second message 48 hours after, and possibly a third message within three or four days of abandonment.