Contrary to old marketing beliefs, using all capital letters in a subject line can significantly increase open rates without negatively impacting deliverability. It's a simple test many marketers avoid due to outdated fears of spam filters.
Subject lines that suggest an internal mistake or conflict, such as "We forgot to end this sale," create a feeling of insider access for the recipient. This "accidental reveal" tactic builds urgency and exclusivity, driving higher engagement.
Challenge your target audience's identity to provoke an open. A subject line like "Not for advanced marketers" piques the curiosity of that exact group, who open the email to prove the statement wrong or see why they are being excluded.
Many marketers mistakenly reveal the entire value of an email in the subject line, killing any reason to open it. To maximize opens, provide a compelling hint or create a curiosity gap rather than giving away the full story.