The Top 20 Email Subject Line Mistakes (and how to fix them)

top 20 email subject line mistakes

The average business user receives 100 to 150 Emails per day. That is a lot of information to sift through on a daily, hourly, and often minute-by-minute basis. One way you can help people process and triage Emails is to craft relevant, concise, and helpful Email Subject Lines.

A good Email Subject line will:

  • Gain the attention of the reader.

  • Quickly communicate important information

  • State the timeline for a response

  • Highlight its relevance to the recipient.

In several prior posts, I presented some “best practices” for Email subject lines.

Among these, included helpful Email Subject Line practices such as:

In fact, a poorly worded Email Subject Line can actually do more harm than good.

It may confuse the recipient as to the relevance of the Email.

It may also cause them to defer it, ignore it, or even delete it without even reading it!

So, here are the Top 20 Email Subject Line Mistakes
(......and how to fix them)!


1. Using CAPS

Everyone knows that the use of CAPS signifies SHOUTING.. so please, just don’t do it!

No one wants an Email that appears to be yelling at them, such as:

"PLEASE REVIEW latest regulations….."

If something is important, you can always use an Email hashtag such as “IMP:” or “STAT:” at the start.

About the only exception would be if the CAPS are for a widely recognized abbreviation , such as:

"Please review latest EPA and FDA regulations and provide feedback by Fri., 10/1."


2. Using Excessive Punctuation

There is no reason to use exclamation points or question marks in a subject line.  

If something is important, use Email Hashtag such as “IMP” or mark the Email Status as "Important".

And unless you are composing a "subject line only" Email as a question, it is best to ask questions in the body of the Email message.

And excessive use of punctuation can make an Email Subject line difficult to read, especially on mobile devices.


3. Using Special Characters or Symbols

Email Subject Lines should not contain special characters or symbols, such as $, %, &, @, and #.  

These are likely to be viewed as “spam” by both the recipient or the Email system's Spam Filter.

If you need to provide details such as dollars or percentages, it is more appropriate to include that in the body of the Email where you can explain this type of item in more detail.


4. Subject Lines that contain spelling or grammar errors

Nothing reads “sloppy” like an Email Subject Line that contains spelling or grammar errors.

Who wants to read an Email if the sender can’t even be bothered to ensure the subject line is free of basic grammar, spelling, or syntax errors.

Always use “Spell Check” when sending out Emails, and don’t forget to check the subject line as well!


5. Excessive use of “RE” and “FW”  in the Subject Line

When an Email gets “replied” or “forwarded” multiple times, you often end-up with an Email Subject line that looks like this:

"FW: FW: RE: RE: RE: RE: RE: RE: Western Sales Report Top Customer Issues"

Do yourself, and your recipients, the favor or removing all the unnecessary “RE” and “FW” from the Email Subject Line.

You will also have more room to add important, helpful, and relevant information to the subject line.


6. Using "Spammy" Words in the Subject Line

Any time people see certain words in the Subject Lines, they are likely to view the message as “Spam”, even if is something legitimate.

Some typical “SPAM” words include:

  • Free
  • Money
  • Win
  • Sign-Up!
  • Now!
  • Bonus
  • One-Time
  • Limited
  • Order
  • Offer
  • Join
  • Percent-Off
  • Millions
  • Cure
  • Only Time
  • Deal
  • Gift

In fact, many corporate spam filters automatically block Emails that contain these types of words so they may never even reach the intended recipients.

For a complete list of “Spammy” Email terms, check out this list of Email Spam Terms on Hubspot.


7. Using a One Word Subject Line

One word subject lines are likely to be viewed as simple "spam" and result in the recipient just hitting the "delete" key.

Examples are subject lines that just read:

  • “Hi”
  • “Important”
  • “Survey”

And if if it isn’t SPAM, it shows a like of concern or professionalism for the content of the message.

So, don’t send out single word subject lines.   Follow good protocol and craft Email subject lines that are helpful and relevant.


8. Overly long Subject Lines

Email subject lines should be concise and to-the-point.

If a subject line is overly long, wordy, or contains redundant information, the recipient may not spend the time to review it and just consider it as “spam” or “noise”.

Keep Email subject lines brief - typically no more than 50 characters or about 8 to 10 words.

This is especially important as more and more Emails are being read on mobile devices where screen space is at a premium.

And remember to always put the most important information at the start of the subject line!


9. Not indicating Urgency

A key piece of information to convey in an Email Subject Line is the “urgency” of a request.  

People want to understand not only whether they need to respond, but also "how quickly" to respond.

Whenever possible, include the required timeline in the Email subject line.

So, instead of saying:

“Respond to issue with Acme Packaging from Customer Survey Results”

Be a bit more specific and say:

“Respond by Fri., 10/1 to issue with Acme Packaging from Customer Survey Results”


10. Not updating the Subject Line when the topic has changed

Often, the topic or focus of the Email conversation will change over time.

But people rarely remember to update the subject line to reflect the current topic.  

For example, perhaps the original Email was about a sales report:

"RE: November Sales Report for Western Region"

But now, the focus of the Email has changed to an issue with a specific customer (Acme Packaging).

At this point, it would be appropriate to update the Email subject line.

You can even retain a reference to the original source, but update the focus to the current issue at hand, such as:

"Acme Packaging Shipping Issues (RE: Nov. Sales Report - Western Region)"


11. Using a personal name if you don’t actually have a personal relationship

Most people consider it “spammy” to receive an Email with their name in the subject line from someone they don't know.

They are likely to consider the Email to be from a “mass mailing” campaign and either ignore it or delete it.

An example of inappropriate use would be:

Mr. Jim Smith- Read how your company can improve its sales revenue by following our simple model

An example of appropriate use of a personal name would be when you already have a working relationship with that person and need to call their attention to an issue, such as:

"Jim - Need you to review this quality report STAT and provide feedback for meeting on Friday."


12. Subject Lines that are Requests for Actions from people you don’t know

Everyone is busy these days… often too busy to be bothered by unsolicited requests that will take up your valuable time and effort.

Unless the Email is from a manager or important individual, no one likes receiving Emails that are making demands on your (very limited) time.

Who wants to open an Email that says:

"Complete this survey NOW or be left behind!"

There they are… just asking for your time and effort with little information as to “why” you should even spend your time doing it.


Instead, Emails should offer something of value hat entices the recipient.  

Look at this more helpful alternative:

"Our survey will help you identify ways to improve sales by 10% with no cost to you!"


13. Misleading Subject Lines

No one likes being misled.

Same goes for Email subject lines.

A subject line should never promise one thing but really be a “ploy” for something entirely different.

Consider an Email Subject line such as:

“CRITICAL:  Read Enclosed Report and Respond to ensure compliance with regulatory changes”

And then the actual Email body is a pitch to sign-up for a webinar or online training class!

This is not honest.  And although you may get the recipient to “open” the Email, you will end-up with an upset reader.

If you had a legitimate offer for a training class, then your subject should state so:

"New Training Program Provides Important Information on Regulatory Changes"

And never start an Email with “RE:” or “FW:” to tr to fool someone into thinking the Email is part of an existing conversation when it is not. This is just plain dishonest!


14. Vague Subject Lines

Avoid “vague” or “unclear” subject lines.

This is not quite as bad as being outright misleading, but is a close second.

An example of vague or unclear subject lines would be:

  • "Need you to review this"
  • "Sales Report attached"

Instead, be more helpful and specific, such as:

“Northeast Q1 Sales Report Attached: Requires your Feedback by Fri., 10/1”.


15. Missing a Subject Line Entirely

Yes.  I have seen this.  Emails that don’t even contain a subject line!

An email with a missing subject line is likely to get missed, lost, or ignored entirely.

This is often done by accident, and many Email systems will provide a “warning” if you attempt to send an Email without  a subject line.

Make sure to avoid this issue, and always use a subject line to help convey the key topic of the Email.


16. Subject Lines that sound like they are “Begging for Attention”

Any Email Subject line that appears to “beg for attention” is likely to be seen as “spammy” and get deferred or ignored.

Examples are Subject Lines that contain phrases such as:

  • “Read this now!”
  • “Limited Time Offer”
  • “Last Chance to Act”
  • “Don’t be left out”

If you have a compelling business proposition, you should make your case in the body of the Email.

The subject line is to communicate the content, not to try to incite someone’s emotions or guilt.


17. Using a Subject Line for Information that should be in the Email Body

The subject line should convey key information contained within the Email, but not replace the Email itself.

For example, if you are applying for a job, don’t use an Email Subject line such as:

“Bob - Requesting an interview for summer position this Friday”

Instead, use the subject line to set the context and key information, but the “ask” should be in the body of the Email.

A more appropriate subject line to the above would be to set the stage for the request, but peak interest in the contents as well:

“Referred by Tom Smith for Summer Intern Position - Resume Attached”


18. Subject Lines that appear to be “system-generated” or from “auto-responders”

If the subject line appears to be something created by an automated system or service, people are likely to ignore it.

An example is an Email that start with:

  • "Your Invitation to Opt-In..”
  • “John - Last Chance to Sign-Up!”.

Even if this was done by a person, it “looks” like something that was ‘auto-generated’ off of a list of names.

So, make sure your subject lines sound like they were written by a human and are customized to the recipient.


19. Not including who referred you

If you are Emailing someone you don't know but were referred to them by a colleague or friend, don’t save that information for the body of the Email.  

That is crucial information to put into the subject of the Email.

It may mean the difference between an Email being read and one that is deleted without being opened.

Consider the difference in an Email that says:

“New Sales Training Program - Free Seminar”


“Referred by Tom Smith - Regional Sales Director:  New Sales Training Program - Free Seminar”

Just make sure you aren’t misrepresenting the referral or relationship.

If I ask Tom Smith, he should vouch for the legitimacy of the referral.


20. Forgetting to tailor the Email Subject Line to the individual recipient

Sometimes, you may use an Email Template for sending out similar messages multiple times.

Whenever you do this, remember to always update the subject line to tailor the message to the new recipient.  

For example, perhaps you have an Email template you use to inform customers of a new training program:

“New Regulations Impact Excise Tax - Free Seminar offer to <insert company name here>"

Now, won’t you feel silly if you forget to update the Email with the actual company name!

So, make sure you always review the subject line (as well as the content!) any time you are “reusing” an Email before you hit “send”.


Email Subject Line Final Words of Wisdom:

The subject line of an Email is like the headline of a letter or the title or an article.  

It should grab the reader’s attention, convey importance, provide key information, and highlight required deadlines.

By following these simple rules, and avoiding these 20 common mistakes, you can greatly improve your ability to communicate effectively and efficiently with others.

You will also greatly reduce the chance your message will be deferred, ignored, or even deleted entirely without being read.


What do you think?

Do you have any other common Email Subject Line Mistakes you have seen?

Learn Email Etiquette by reviewing helpful books and resources: