Capitalization in Email Subject Lines: What Works

The subject line decides whether an email is opened, ignored or reported as spam. Capitalization is a small detail that affects both tone and trust.

Sentence case or title case?

• Sentence case ("Your order has shipped") feels personal, like an email from a real person. Many brands find it suits transactional and newsletter emails.
• Title Case ("Your Weekly Marketing Roundup") feels more like a headline, which can suit editorial newsletters.

There is no universal winner. Test both with your audience and keep the style consistent once you choose.

Avoid all caps

Subject lines written entirely in capitals look aggressive and are a classic spam signal. Even a single word in capitals, such as "FREE", can feel pushy. If you need emphasis, use a specific benefit instead: "Free shipping ends tonight".

Other subject line tips

1. Front-load the important words. Mobile inboxes may show only around 30 to 40 characters.
2. Be specific. "3 ways to cut your heating bill" beats "Our latest tips".
3. Use preheader text to extend the message.
4. Avoid excessive punctuation such as "!!!" or "???".
5. Personalize carefully; the recipient's name is only useful if it adds relevance.

Check length and case quickly

Draft several subject lines, then:

• Paste them into a character counter to check length.
• Use the case converter to switch between sentence and title case and compare.

Measure, then decide

Your email platform's A/B testing feature is the best judge. Test one variable at a time, such as capitalization style, on a large enough list to get a meaningful result.

Frequently asked questions

What is the best capitalization in email subject lines?

For capitalization in email subject lines, sentence case usually feels personal and title case feels editorial. Avoid all caps. Test both styles with your audience.

Can a tool capitalize my title or subject line?

Yes. Paste your subject line into our headline capitalization tool and choose Title Case or Sentence case. It works as a quick "capitalize my title" helper and title case generator. You can also convert to title case online for any headline.