The subject line is the “front door” of your email. If it doesn’t look inviting, your subscribers won’t enter—no matter how great the content inside is. On average, 33% of people decide whether to open an email based on the subject line alone.
1. Keep it Short and Sweet
Most people check their emails on mobile devices. If your subject line is too long, it will get “cut off,” and your message will be lost.
- Ideal length: 40–50 characters.
- Mobile focus: Put the most important words at the beginning.
2. Use the “Big Three” Psychologies
The best subject lines usually tap into one of these three human emotions:
- Curiosity: “I have a weird secret to tell you…” (People hate not knowing).
- Urgency: “Only 4 hours left to grab this.” (FOMO – Fear Of Missing Out).
- Direct Benefit: “How to save $500 on your next flight.” (Clear value).
3. Avoid the “Spam Trigger” Trap
Certain words are like “red flags” to Gmail and Outlook filters. If you use them too much, you’ll end up in the junk folder.
4. Personalize with Tags
In Send Onyx, you can dynamically insert your subscriber’s name into the subject line. An email that says “Hey John, check this out” will almost always outperform one that just says “Check this out.”
- Usage: Use the
[first_name]tag naturally. Don’t overdo it, or it will start to feel “robotic.”
5. Test Your Ideas
Before you blast your entire list, think about A/B Testing.
- Send Subject A to 10% of your list.
- Send Subject B to another 10%.
- The winner (the one with the most opens) gets sent to the remaining 80%.
Summary: Your subject line is a promise. Make it interesting enough to open, but honest enough that the subscriber isn’t disappointed when they read the actual email.