5 Most Common Email Subject Line Mistakes to Avoid At All Costs

The 5 Most Common Subject Line Mistakes to Avoid

So you’ve just put your finishing touches on that latest blog post, new YouTube video that you know is going to really help all those people on your list, your audience, though upon checking your open rates on your email service provider account, you’re quietly devastated at your low open rates. It hurts doesn’t it!

Where are the best subject lines? In your inbox! What makes you click on an email to open it?

Advertising legend David Ogilvy once said: 

Five times as many people read the headline as read the body copy. When you have written your headline, you have spent eighty cents out of your dollar.

Like a headline for a blog post or news article, the subject line for your email needs to capture people’s attention and convince them to open your message. A subject line can make or break the performance of your email, so it’s important to spend extra time crafting one that’s memorable and effective.

Good subject lines get to the point, create a sense of urgency and are relevant to the subscriber, but it’s easy to make mistakes when writing them. Committing these subject line sins can drastically reduce your open rates, but avoiding them is easy if you know what to look for.

Here are five of the most common mistakes people make when writing email subject lines, as well as tips to improve them and boost your open rates.

1. Using ALL CAPS or too much punctuation(!!)

Imagine receiving an email with a subject line like this in your inbox: GET 70% OFF YOUR NEXT PURCHASE RIGHT NOW!!!!!!!!!!!!!!!!!!!

Chances are you would take one of three actions: ignore it, delete it, or mark it as spam.


It can come across as though you are yelling, which can have a negative impact on your email performance. So you should use capitalisation and punctuation cautiously. 

Occasionally adding phrases like “Free” or “Act Now” have been shown to improve open rates, but I recommend using them sparingly to avoid diluting their impact. 

On a similar note, be sure to avoid using too much punctuation. You have limited real estate for your subject line, and multiple exclamation marks can come across as spammy. Special characters such as * % & # and ^,  have been known to trigger spam filters, so be sure to use them sparingly as well.

Now that we’ve gone over the punctuation mistakes to avoid in your subject line, you may be wondering which characters leads to more open rates.

The answer? Question marks, exclamation points and periods. 

Subject lines with exclamation points can expect an open rate that’s one to 20 percent higher than average – just as long as you don’t use them in every message.

While this can vary depending on your industry, your audience, and the content of your messages, I recommend testing multiple subject lines to see which forms of punctuation your subscribers are more likely to respond to.

By using simple language, asking a question, and using proper punctuation in her subject line, you’re able to pique the reader’s interest and entice them to read your message.

Exclamation points, periods, and question marks are all part of a healthy email marketing strategy, so don’t be afraid to mix up the punctuation you use in your subject lines.

2. Using Spammy Words

Adding certain trigger words to your subject line can activate a recipient’s spam filter, even if the message you’re sending is legitimate.

To prevent this from happening, avoid symbols like “$$$,” “100% free,” “cash off,” “cheap,” “weight loss,” and “serious cash”. Even if your email makes it into the inbox, it can come across as spammy to your subscribers.

To ensure your readers take your emails seriously, choose the language of your subject line carefully by avoiding some of the trigger words and symbols listed above.

Finding the right verbiage for your subject line can be tough, especially with the sophisticated spam filters out today. HubSpot put together an exhaustive list of email trigger words to avoid when composing your subject line, so reference it before sending your next message.

While there are plenty of recommendations for words to avoid in subject lines, there’s no hard and fast rule for ones to include; what works for one industry may not work for another. Be sure to try different variations of words to see what resonates best.

I also recommend focusing on specific words that tie back to the content in your email.

The subject line tells you exactly what you’ll get by opening up the email. And by focusing on that, it eliminates the risk of including words that might appear spammy.

3. Making It Too Long

Consider the environment in which your subscribers are reading your emails. Chances are, they’re on-the-go or quickly scanning their inboxes between work meetings.

Since you have only seconds to capture their attention, you want to make sure your subject lines aren’t wordy or redundant.

Long subject lines look spammy and get lost in cluttered inboxes, especially if readers are using mobile devices.

One favorite rule of thumb is  to keep subject lines no longer than 50 characters. To do so, aim to get your message across as quickly as possible and cut any unnecessary terms or phrases.

As important as it is to get your message across quickly and clearly, make sure it expresses a complete thought and offers value to the reader – you don’t want to write a subject line that’s too short, either. Avoid one-word subject lines and strive to be helpful and relevant to your subscriber.

Try building a message around a numbered list and including the word “secrets,” As a result, this subject line is easily readable and irresistibly clickable!

4. Writing misleading content

Let’s say you send an email with the following subject: Get an exclusive 50% discount on our entire inventory!

But when the reader opens the email, it’s a pitch to sign up for a webinar or free online class.

Not only is this tactic dishonest, it also tends to backfire. No one likes to be deceived, especially when they receive an email that promises one thing and delivers another. You might get people to open your email initially, but this alienates subscribers and can hurt your open rates and spam rates in the long run.

If your subscribers lose trust in your emails, they’re more inclined to ignore future emails and mark you as spam.

To build and maintain trust between you and your subscriber, make sure to align the content of your email and your subject line.

Also avoid subject lines that include RE: or FW:

These tend to trick the reader into thinking the email was part of another conversation, which doesn’t leave a positive feeling with subscribers.

Not including this text also gives you more room to work with in your subject line, which can be used to convey helpful and relevant information instead.

5. Including spelling or grammatical errors

Subject lines (or any other content in your email) with typos, misspelled words, and misplaced punctuation look unprofessional and can hurt your open rates.

Emails are an opportunity to establish your brand as a helpful source of information. Subject lines with spelling or syntax errors make a bad first impression, and undermine your ability to establish trust with your subscribers.

To optimise your email open rates, be sure to review your emails for grammar and spelling prior to hitting send. No one will take the time to read your email if the subject line is loaded with grammar mistakes, but basic copy editing can prevent these errors from slipping through the cracks.

Crafting subject lines that sweep subscribers off their feet…

The subject line is one of email’s most important components, so it’s important to get it right before you send your emails. And by avoiding the mistakes above, you’ll be well on your way towards improving your email engagement.

I really hope this helped. Hey, have I missed anything here though? Drop me a note in the comments section below and let me know your thoughts. 

Do you have any subject line best practices that weren’t listed in this post? I’d love to hear about it in the comments below!


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About Phil

Phil Adair is the host of one of the most downloaded online marketing podcasts on the internet. (Go here to subscribe and listen to The Online Marketing Strategies Show.)

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Ocean Plastic Pollution?


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My new course list building tornado is currently in production. Excited about the launch. I will keep you updated, though if you want little tasting plate straight away, then download the free eBook which has 27 Powerful Techniques For Growing Your Email List… fast!!!


Today’s episode is all about… well it’s abbreviated purposely and designed to agitate your brain. I want you to get angry… Though, before we get to that…


What ticked me off on holiday?


Ok, got to stop: Thanks for reaching out? I want you to pull me up on this if I ever say it…together we can do this.


Its super oily and slimy, sounds like someone I paid to read my tarot cards might say…It sounds clingy, insincere and way too false and flakey…It’s trying too hard to be your friend, and way too early in the conversation by the way to start… well, reaching out…


Can you please email me via my website at hotclicks.com.au shortly to become Philadair.com and tell me if I need psychological assistance, or on the other hand, are you in agreeance with me on this one? What other kind of repetitive verbal battering is rumbling around inside your grey matter?


How about the: “So, here’s the thing…” pre-empting every second sentence. Overused people, and starting to make you sound bit one dimensional if you want to know the honest truth…


Now what really, really bothered me… (cue the sinister music.) I ‘m getting serious here folks…


As Marc Maron would say on his podcast show… What the Fuck?? Or as Mary Steenburgen said on Stepbrothers: What the Fuckin’ fuck? How many miles is it to the deepest part of the ocean?



I’m glad you asked. The deepest part of the ocean is in the Mariana Trench (sometimes called the Marianas Trench), located in the western Pacific Ocean. At its deepest part, it’s just less than 7 miles (6.831 miles / 10.994 km / 10,994 meters) deep.


How many marine animals are killed by plastic each year? Around the world, an estimated one million birds and 100,000 marine mammals and sea turtles die each year when they become trapped in plastic or eat it, perhaps mistaking it for a tasty treat. It is one of biggest threats to all whales and dolphins occurring throughout the world’s oceans.


How long does it take for a plastic bag to decompose in the ocean?


Plastic bags can take 20 years to decompose, plastic bottles up to 450 years, and fishing line, 600 years; but in fact, no one really knows how long plastics will remain in the ocean. With exposure to UV rays and the ocean environment, plastic just breaks down into smaller and smaller fragments.



Plastic rubbish will outweigh fish in the oceans by 2050 unless the world takes drastic action to recycle the material, a report has warned on the opening day of the World Economic Forum (WEF) The share of leakage into the ocean is at least 8 million tones, equal to one garbage truck-full every minute, and research estimates that there are more than 150 million tones in the ocean today. If no action is taken, this is expected to increase to two [truck-full’s] per minute by 2030 and four per minute by 2050,” the report said, with packaging estimated to represent the largest share of the pollution.


In a business-as-usual scenario, the ocean is expected to contain one tone of plastic for every three tones of fish by 2025, and by 2050, more plastics than fish,” it said. A sweeping change in the use of plastic packaging would require cooperation worldwide between consumer goods companies, plastic packaging producers, businesses involved in collection, cities, policymakers and other organisations, the report said.


It proposed creating an independent coordinating body for the initiative. Rather than spend way too much time trying to convince their respective governments… I feel we need to approach this on a different tack. 


How about a company funded by Billionaires (hello Elon, Hey there Richard Branson, Good morning Bill Gates, Whats up Mark Zuckerberg, Warren Buffett, are you going to do anything? Can you spare a dime?


If we don’t address this now, and stop pretending it’s high on everyone’s agenda when it’s not, by 2050 you and me and those that follow us will be royally screwed. Irreversible damage, again those two words: irreversible damage. Fuck the oceans and this planet dies… So  Readers and listeners… I need your help. Can we do this I hear you asking? Well, of course we can… you and I, us, fellow human beings, we have a moral responsibility for those that follow us into this life to show them we actually care.


What can we do together? Start messaging me and give me your ideas. Please! If you’re not passionate about this cause, that’s okay, no judgement from Phil Adair. I promise.


If we can build a flotilla of gigantic catchment boats with equally gigantic sifting arms, that roam the ocean 24/7 powered contentiously by solar panels unmanned robotic rechargeable electric Tesla ships, I believe we can absolutely avoid the very real, possibility of global decline.


This is now our greatest ever challenge. Yes, today was a diversion, though I feel a very necessary one. The people we love the most are depending on us folks.That’s it. Let’s do this. I’ll see you soon.

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428 George Street, Sydney 2000, NSW, Australia  

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I’m a huge fan of connecting on social media. If you’re on these social networks, then let’s follow each other: 








About Phil Adair

Phil Adair is the host of one of the most downloaded online marketing podcasts on the internet (go here to subscribe and listen to The Online Marketing Strategies Show.)

Read his inspiring bio now.  Feel free to send Phil a message here.