Email subject line best practices

Most of your subscribers will see your subject line on a phone, which means they see about 40 characters before it gets chopped. And they're deciding in a split second whether you're worth opening or deleting. The subject lines that win sound like they came from a person, not a marketing department.

• Put the payoff in the first five words. If the good part comes after the cutoff, it may as well not exist.
• One idea per subject line. The moment you cram in two, both get weaker.
• Skip the spam bait. Words like "free," all caps, and exclamation points get you filtered before a human ever sees you.
• Your preview text is a second hook. Don’t waste it on "View this email in your browser."
• Try lowercase. A subject line like "quick question about tuesday" reads personal, and personal gets opened.

The mistake I see most often is writing the subject line last, as an afterthought, once the email is done. Flip that. Write five subject lines before you write the email, pick the strongest, and let it shape the message. The second most common mistake is being clever instead of clear. A puzzle in the inbox doesn't feel intriguing, it feels like work, and work gets deleted.