How to write effective internal email subject lines

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.

Guideline: Aim for subject lines less than 42 characters long or up to 7 words to ensure they’re visible across devices and email clients.

Examples: 

• 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)

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 

If you want to optimize your subject lines, it’s essential to experiment with different options. Traditional A/B testing sends one version of a message to a portion of the audience and sends the best-performing message to the remainder.

First, you randomly split your list into three groups. Then, you compose two subject line variations for each test email group. You will likely need about 250 recipients in each test group to be statistically valid. Wait an hour or two after the send to gather enough measurement data. Then, choose the subject with the highest attention rate and send that to the reminder groups. This process takes time and planning but may boost your results.

Why it Matters: One of the hallmarks of a good communication strategy is having benchmarks to determine what your audience responds to. Trying out various subject lines on different audience segments will reveal how you should be writing them.

Guideline: Choose an email campaign or newsletter to monitor with different subject lines to see what kind of engagement your audience prefers.

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. 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!