Email Subject Etiquette 6 Rules: How To Subject Best

The crucial email subject etiquette for making your emails more effective. How to choose an appropriate and effective subject.

What email subject etiquette is

Email subject etiquette is the set of rules to write polite, clear, and effective subjects for your emails. Such rules help us increase the effectiveness of our emails by building trust with the recipient and avoiding behaviors that may make us look impolite. They include:

  • How to write an appropriate and effective email subject.
  • The mistakes to avoid.

When you send an email, follow the subject etiquette rules to increase the chances that the recipient reads the email and perceives its tone and message correctly.

how to write an effective email subject

Email subject etiquette rules

1) The ideal email subject is clear and useful

Recipients are more likely to trust an email when they can tell what to expect from it. Thus, an effective subject must be clear to understand and anticipate the content of the message. When reading the subject, the recipient should be able to tell what the message is about, its tone, and the type of action it requires.

Thus, if the message is an update, it is perfect etiquette to state “update” in the subject. If the email requires the recipient to make a decision, the subject can include “decision”.

For example: “Decision: next weekend” informs the recipient that the email is about deciding something regarding the next weekend.

2) Make it vivid and keep it short

Follow the principles of business writing, such as avoiding filler or weasel words. Try to use only vivid words and avoid adverbs or adjectives. If appropriate, include numbers or data that the recipient will understand.

The email subject must be short. On the one hand, it has to convey the message. On the other hand, it must be easy to visualize on a small screen.

3) Avoid misleading subjects

A misleading email subject breaches trust and can make your email ineffective and even damage your reputation.

Before sending an email, ask yourself if someone may interpret your subject differently. In other words, is it possible that the recipient misinterprets the email intent when reading the subject? If the answer is yes, change the subject. A long and dull subject is preferable to a misleading or incorrect one.

4) Avoid vague or blank subjects

A blank or vague subject can upset the recipients, as it is impossible to anticipate the content of the email. Furthermore, it conveys sloppiness and laziness, like you did not care enough to invest one minute to choose a good subject line. At work, it can make you look unprofessional and ineffective. In your private life, it can make you look immature and careless.

Thus, it is best to always include a subject and never leave it blank. Similarly, avoid vague subject lines and generic words. Such as “Hi”, “How are you”, “FYI”, or “Update”. Instead, add some context with a few words. For example, “FYI – fundraising” or “Update on the new product”.

5) Limit the use of URGENT in the email subject

In the email subject, it is best to avoid words such as URGENT, Please read, ACT NOW, or similar. It is rather impolite and can make your email ineffective.

First, this type of subject risks putting the recipients in the wrong mood to read your email and correctly interpret its content. Second, these subjects imply that all your other emails are not urgent or worth reading.

When you need to deliver an urgent message, do not write an email. Instead, choose a faster and more effective communication channel, such as calling, going in person, or sending a text message.

6) Do not change the subject of an email

When replying to an email, it is impolite and inefficient to change its subject. First, it will confuse the recipients, who may believe that the email belongs to a new conversation. Second, it can offend the original sender, who may think that you are correcting the subject and perceive you as arrogant.

email subject etiquette worst mistakes

Email subject etiquette: the worst mistakes

The Rude Index identifies and ranks negative behaviors. 

A high score (8-10) means that the behavior has the potential to trigger a conflict with others. A medium score (4-7) means that the behavior risks making you look inelegant and unsophisticated. Read more about the Rude Index and its methodology here.  

Avoid the worst email subject etiquette mistakes: 

  • 8/10. Writing a misleading subject.
  • 7/10. Changing the subject of an email thread.
  • 4/10. Writing an unclear subject.
  • 4/10. Sending an email without a subject.


  • The Effect of Subject Lines on Open Rates of Email Marketing Messages: