Demographics: Certain demographics like age, gender, job title, and other information that informs your buyer personas can be a good way to segment customers and customize messages. For example, a financial company may want to send retirement-themed emails to customers seeking information on offering their employees benefits and emails about college loans to university-based customers.
When it comes to deciding how to craft that perfect subject line, there appears to be really only one area to avoid: the subject line of 60 to 70 characters. Marketers refer to this as the “dead zone” of subject length. According to research by Adestra, which tracked over 900 million emails for its report, there is no increase in either open rate or clickthroughs at this 60-to-70 character length of subject line.