What is an email subject line?
An email subject line is the short line of text recipients see before opening an email. It acts as a preview of the message and helps readers decide whether an email is relevant, urgent, or worth opening.
For internal communicators, subject lines are especially important because employees receive dozens of emails each day. A strong subject line can improve open rates, increase employee attention, and encourage faster action on important communications.
Whether you are sending a company announcement, newsletter, HR update, or leadership message, the subject line often determines whether your email gets read.
Why email subject lines are important
Subject lines are an underappreciated asset.
Internal communicators devote significant effort to crafting the content of employee emails, such as announcements, news updates, and safety memos. Yet, the subject lines are often just an afterthought.
Since subject lines contain a lot of power, this is an unfortunate oversight. To name a few benefits, an effective subject line can:
- Capture the recipient’s attention.
- Motivate a recipient to take action.
- Spark interest and curiosity to read the content of your email.
Generally, people filter their limited attention based on who the message is from and what it is about. Subject lines provide context for the about.
Let’s examine five best practices that can help optimize your internal email subject lines.
Best practices for subject lines
Best Practice 1: Keep subject lines concise, but interesting
Why it Matters: Depending on an employee’s email client or device, long subject lines are often cut off over 42 characters, losing their impact. To avoid the possibility of an email client truncating your subject line, keep it concise yet engaging. PoliteMail’s benchmark data reveals subject lines of 5-7 words have the highest engagement.
How long should an email subject line be?
The ideal email subject line length is typically between 5–7 words or under 42 characters. Shorter subject lines are easier to scan and are less likely to get cut off on mobile devices and email clients.
However, clarity matters more than strict length. A concise subject line that clearly communicates value will usually outperform a vague or overly clever one.
For example:
- Poor: “Important Information Regarding the Upcoming Team Meeting” (57 characters and dry)
- Good: “June Team Meeting Details” (25 characters but dry)
- Best: “June Recap: We Survived!” (24 characters with personality)
When possible, place the most important information at the beginning of the subject line so readers see it immediately, even if the text gets truncated.
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Best Practice 2: Allude to the contents of the email in your subject line
Why it Matters: People receive an average of 121 emails each day. Since your employees need to triage their emails efficiently—quickly deciding which messages are urgent and which ones can wait—it’s essential that they can easily grasp why your message is relevant and what value it may include. Write subject lines that are easy to scan and understand at a glance.
Guideline: Choose simplicity over creativity. No one likes boring, but you don’t want creativity to complicate or confuse your subject line. Simplify your language, eliminate extra words, and lead with specific information.
Examples:
- Poor: “Company News” (generic)
- Good: “New Office Perks” (more specific but still vague)
- Best: “Casual Fridays Return!” (fun and specific)
Best Practice 3: Tell people if they need to do something in your subject line
Why it Matters: Subject lines that include a “to-do” item can prompt employees to open the email sooner rather than later. If you need a response to an email, especially if there is a time-sensitive deadline, ask for it in the subject line. You can literally write, ‘Response Requested.’
Guideline: Use action-oriented language that suggests a time-sensitive need or opportunity. PoliteMail’s benchmarking data reveals some of the best action words are “Update, News, Action, FYI, Required, New, and Important.”
Examples:
- Poor: “Submit Reports Soon”
- Good: “Report Submission Due Friday”
- Best: “Action Required: Security Form Due 8/1”
Best Practice 4: Personalize your subject lines when possible
Why it Matters: Personalized subject lines can make emails feel more relevant to the recipient, increasing the likelihood of engagement.
Guideline: Write subject lines with the recipient’s name or relevant details.
Examples:
- Poor: “Team Achievements”
- Better: “Your Team’s Achievements”
- Best: “Congrats, [Name]: You’re a Rockstar!”
Best Practice 5: Implement traditional A/B testing
Why it Matters: A/B testing helps internal communicators identify which subject lines generate higher open rates and employee engagement.
How to A/B test email subject lines effectively
- Split your audience into three random groups.
- Create two versions of your subject line.
- Send each version to a smaller test group.
- Wait one to two hours to gather performance data.
- Send the winning subject line to the remaining audience.
For the most reliable results:
- Test only one variable at a time.
- Use a large enough audience sample.
- Avoid changing send times during the test.
- Measure open rates, attention rates, and click engagement.
Over time, A/B testing reveals patterns in the language, tone, and structure your employees respond to most often.
Leverage PoliteMail’s Ai/B tool
PoliteMail includes a Subject Line Suggester feature, leveraging AI predictive analytics to instantly perform multiple A/B tests, allowing you to send one strong email broadcast with an engaging subject line. After you draft a subject line, this tool provides alternatives tested and ranked by PoliteMail’s predictive analytics model, optimized for attention rate. You can modify the suggestion, conduct an instant test, or ask for other recommendations.
Newsletter email subject line examples
Newsletter email subject lines should create curiosity while clearly communicating value. Employees should immediately understand what kind of updates, news, or insights the newsletter contains.
Effective newsletter subject lines often include:
- Timely updates
- Employee-focused benefits
- Numbers or lists
- Friendly conversational language
- A preview of valuable information
Examples of effective newsletter subject lines include:
- “5 Updates You Need This Week”
- “What’s New Across the Company”
- “Your Monthly HR Highlights”
- “This Week’s Employee Spotlight”
- “Top Team Wins From May”
Avoid generic newsletter subject lines like “Company Newsletter” or “Monthly Update,” which do little to encourage engagement.
Write better subject lines
Effective subject lines will increase your readership by garnering interest in your message. A well-crafted subject line can be the difference between getting someone to read your email or not. It’s also an opportunity to set the expectation of what you want the recipient to do.
Catchy email subject lines increase open rates because they quickly communicate relevance, urgency, or curiosity. The best subject lines balance clarity with personality. Instead of relying on vague clickbait tactics, focus on writing subject lines that are specific, employee-focused, and easy to scan. Even small wording changes can significantly impact engagement.
Make your subject lines concise yet engaging, direct, action-oriented, and personalized. Leverage new AI tools to brainstorm alternative subject lines and automatically and instantly A/B test variations to discover which line will most likely get your employees’ attention. And remember, a little fun goes a long way in making your emails stand out!
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