Email Subject Line Capitalization: How to Choose the Right Case

Email Subject Lines: Your Ticket to Inboxes

Your email’s subject line is super important. This is the first thing everyone sees in their inboxes. But with different ways to write it, how do you pick the right one?

The email subject is a ticket to numerous inboxes. But how to write such phrases that will attract attention and make people open your messages? With a little creativity and smart thinking, you can turn your emails from boring to great!

This article is here to help you understand how to choose the best capitalization style for your subject lines. Whether you’re selling something, sharing news, or just saying hello, the way you write it matters.

So let’s make your emails impressive every time.

How to Capitalize Email Subjects?

When considering capitalization in email subject lines, it is helpful to draw parallels with capitalization in headlines in writing and journalism. Just like in articles or headlines, the purpose of capitalization in email subject lines is to highlight keywords and convey clarity. In both cases, consistency is crucial for readability and professionalism.

However, while traditional writing often adheres to strict style guidelines, such as AP or Chicago style, subject lines in email allow for more flexibility. While heading case is common in journalism and formal writing, sentence case is often preferred for email subject lines because of its simplicity and readability.

Ultimately, the choice between the two depends on your audience and the tone of your message. Whether you choose a headline or a sentence case, the key is to make sure your subject line effectively conveys the essence of your email, encouraging recipients to open it.

Email Subject Line Capitalization Cases

Deciding whether or not to capitalize your subject line is a bit of a puzzle. Your subject line, along with dozens of others, is the first thing recipients see in their inbox, so it’s crucial that it’s catchy and leaves no doubt about whether or not to open it. Capitalization adds a touch of professionalism and makes the text clearer. It helps to emphasize important words or phrases, increasing the chances that your email will be opened. Besides, adhering to a single capitalization style sets your corporate tone of communication with customers.

Email subject lines can vary depending on your company’s preferences, context, and audience. Here are some common cases of capitalization in email subject lines, with our advice on whether or not to use them:

1. Title Case (also known as Headline Case): “We’re Updating Our Customer Agreements”

In this style, the first letter of each main word in a sentence is capitalized. The main words include verbs, nouns, adjectives, adverbs, and pronouns. When articles, conjunctions, and prepositions are usually not capitalized unless they are the first word in the subject.

It is perfectly acceptable to use the headline case in the email subject line, as it can make the subject look more polished and professional, especially if it is used in formal or business letters.

2. Sentence case: “Share your experience for a chance to win a gift card”

It is fair to say that this is the most common style of email subject capitalization, where only the first word is capitalized also with any proper nouns (particular person names, locations, organizations, specific names of the months, etc.). Subject lines written in the sentence case are believed to be more visually appealing and enticing to readers, making it more likely that recipients will open the email.


Do not listen to those who advise you to write so for emphasis or urgency, never write in all caps style because you risk triggering spam filters and ending up in the spam folder.

4. lowercase: “important updates regarding quarterly report”

Not a good decision. This type is considered informal and can be rarely used just for some stylistic effect.

5. Alternating case: “YoUr DiScOuNt Is StIlL WaItInG FoR YoU”

It’s a very bad choice. Alternating case, where each letter alternates between uppercase and lowercase, may catch the eye, but it is more often perceived as unconventional, unprofessional, and difficult to read. We also don’t recommend using this style, as it can appear spammy and cause deliverability issues.

Remember to consider the tone and purpose of your letter when choosing the appropriate capitalization case and don’t forget that according to statistics 69% of recipients’ spam reports are based on the email subject line.

How to Change Subject Line Case Easily in One Click?

If you open your inbox, it’s easy to see that the senders’ subject lines are completely different by content, but they all have one thing in common: they’re written in either Sentence or Title Case. This is the answer to what to choose, pick one of these two and don’t hesitate, and we’ll show you how to do it quickly in the most popular word processors.

Useful Tip:

Did you know that it’s very convenient to format the font and change capitalization in Google Docs in one step? Simply open a document with the email text on your computer, select the part of the Subject Line you wish to modify, click on “Format Text”, and then choose from lowercase, UPPERCASE, or Title Case.

Format Text

To format a font and adjust capitalization in Microsoft Word, navigate to the Subject Line text you want, select it, and then use the Font section of the Home tab to change its appearance and capitalization as needed by choosing the appropriate case from the drop-down list in one click.

Font section

Email Subject Line Capitalization: Famous Style Guides

By the way, we’ve already created an article for you on how to write awesome subject lines. And now let’s move on to the part for those who want to delve into the intricacies of writing and learn about global standards.

There are various style guides that writers around the world follow when creating headlines. These descriptions serve as standardized sets of rules and conventions for writing and formatting in various fields and contexts for clarity, consistency, and professionalism in written communication.

Most of these style standards are descriptive, they just give guidelines based on how people in different fields usually use the language, rather than dictating rules for how you should use it.

Here are examples of email subject capitalization in various style formats for you to familiarize yourself with:

AMA Style (American Medical Association):

This style, commonly used in medical and scientific spheres for clarity and ease of communication, employs the sentence case where only the first word and proper nouns are capitalized.

NY Times Style:

New York Times style typically follows the title case, where the first letter of each major word is capitalized. It’s often used in journalistic writing worldwide to create headlines that are engaging, informative, consistent, and readable.

AP Style (Associated Press):

It is the standard style for news writing and journalism in the United States. Associated Press favors the sentence case for email subject lines, emphasizing brevity and clarity.

APA Style (American Psychological Association):

APA style, frequently used in scientific and academic writing, adheres to the sentence case for email subject lines. It aims for precision and objectivity in presenting research findings and scholarly arguments.

The Chicago Manual of Style:

Chicago style is probably the most used American guide for writing and publishing. It allows for both sentence case and title case, depending on context. This manual is commonly used in publishing and academic writing, offering flexibility while maintaining consistency.

The Elements of Style by Strunk and White:

This manual contains fundamental principles of composition, grammar, punctuation, and style. It emphasizes brevity, clarity, and simplicity in writing, promoting conciseness and accuracy. It has become a classic reference for writers, students, and professionals seeking to improve their writing skills and communicate effectively.

Bluebook Style:

Bluebook style, predominantly used in legal writing, often employs the sentence case for clarity and conciseness. It emphasizes precise citation and adherence to established legal conventions.

MLA Style (Modern Language Association):

MLA style typically follows sentence case for email subject lines, aiming for clarity and coherence in presenting literary and humanities-based research.

Wikipedia Style:

Wikipedia style favors the sentence case for email subject lines, aligning with its collaborative and accessible approach to sharing information. It emphasizes neutrality and verifiability in content creation.

There are no direct guidelines for writing email subject lines in these styles, but they do have general guidelines for text and headings that can be useful for email marketers as well.

Summing Up

Almost half, namely 47%, of email recipients open an email based on the subject line alone. That’s why testing and adapting email title capitalization and content is a strategic step throughout your campaign, as there’s always a chance to increase engagement with your contacts.

In this article, we’ve looked at the most popular email subject line styles and which case is best to choose. So follow our useful tips and get to the inbox as soon as possible!

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Khrystyna Sliusar

Content Lead at GlockApps