1. Keep them short
2. What’s in it for them?
3. Test, test, test
4. Highlight helpful content
5. Don’t be misleading
Keep your subject lines short. I’ve tested this again and again and consistently find that shorter subject lines outperform longer ones. Our attention spans are shrinking every day, which applies to how much time we want to spend reading a subject line as well. Figure out exactly what it is you want the email to accomplish and boil that down into your subject line.
What’s in it for your audience? Put yourself in the recipient’s shoes and think about what you would respond to. Are you offering a $100 gift card to a random winner? Go with a subject line that mentions the prize instead of the more generic “April 2017 Monthly Update.”
That said, you might find that the stable and generic “Monthly Newsletter – April 2017” works best for your audience. I recommend that you test, test, test. Most email software makes this dead simple, so there’s no excuse for portioning off a slice of your subscribers to see what they respond to before emailing the remainder.
Highlight helpful content in the subject line. Send your subscribers information that will help them accomplish something and appeal to their sense of getting things done. Your subject line should tantalize them with visions of all the things they’ll learn inside the email, like “Tips for fixing drains in under 5 minutes” or “7 ways to optimize your email marketing.”
Finally, even though you’re trying to maximize the number of people who open your emails, resist the temptation to go with a misleading subject line that aims to trick people into opening. (Example: “You accepted an offer” or “You won our contest.”) You’ll get opens but it’s likely that you’ll get angry customers as well.