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Best subject lines for sales emails: some examples and keys to success

Vincenzo Ruggiero author on Overloop the sales engagement, cold email, and LinkedIn automation software blog
Vincenzo Ruggiero Apr 27, 20225 min read

The subject line of an email is the first visible text from the inbox by the subscriber, which will indicate what the content of the received email is about. In this short line of text, of just a few words, we must be able to concentrate a key message, an idea that encourages the recipient to open the email and see what we have to offer in the text of the message.

The subject line is one of the first three visible elements, along with the pre-header and sender’s name, that a user will see without opening the email. Hence the importance of optimizing it well, because the success rate of openings of our cold email campaigns will largely depend on the subject line of the message.

Why is it important to write a good subject line?

When writing an email for your target audience, you should always attend to a series of questions such as its content, but the most important thing for the first initial impression is the subject. The subject of an email is the line visible from the inbox by the subscriber, which will indicate what the content of the received email is about.

As I said before, the subject line is one of the three elements visible to the naked eye, which a user will see without having to open the email. It has a fundamental impact on the first impression that your prospect will have about your email and, therefore, if it catches his attention, he will decide to open it and we will have achieved our objective. But, on the contrary, if the subject is not capable of capturing the interest of your prospect, he may directly ignore it and decide to send your message to the trash, without further ado.

We are all used to receive a huge amount of emails and here is a vital factor: time. We have limited time and we only pay attention to what is vital and interesting. Therefore, the subject line of your cold email has to stand out, it has to be knocking on the door of your potential client saying “open me”.

I’ll be clear: the subject line is the number one priority if you want to succeed in your next email marketing campaign. And, to make things a little easier for you, below I am going to explain how to enhance this section to minimize the bounce rate of your cold email campaigns.

Before you start writing the subject line

To start writing, you first have to know what is the goal for which you write. This will allow you to adapt not only the subject line, but the entire content of the email. Here are some ideas, so you can clearly define what you intend to achieve with your next email campaign.

  • Define what you are selling. A product, a service, promotions associated with the previous two….
  • Define your target audience. This will give you a clearer vision of where you want to go
  • Set the purpose of the email. What are you sending it for? What action do you expect from the recipient? Respond to your message, fill out a registration form, access your website... be specific.
  • Who do you send it to? It is not the same to send an email to a person for the first time, than to someone you send messages to frequently. You should moderate your language and ways of speaking depending on who you are writing to.

Important factors when writing the subject line of your email

When preparing a subject line, you must take into account a series of factors that affect the writing of the email:

  1. Generate Interest

    This is the factor that we can influence the most, depending on what we do. To generate interest, you must make your prospect sense the benefits of your proposal and increase their curiosity and their desire to read your complete message.

  2. Relevance

    This factor has a lot to do with the continued opening, with the engagement of your contacts with the emails and about their experience with your emails. When opening the message, is the subject delivering the content it promises? Is there a healthy relationship between subject and email?
    To address these issues, it is very important that the email meets the expectations generated. Otherwise, it will bring users frustration.

  3. Reputation

    Reputation is a long term influencer. To build it in a positive way, you should focus on increasing the relevance of your messages and lowering the frustration of your prospects when reading your content. Again, this is a factor more related to long-term relationships with your prospects, but you must assess it from the outset if you want the success rate of your email marketing campaigns to be adequate.

  4. Urgency

    It is important, in some cases, to use this factor to optimize your subject lines, mainly in cases of promotions or specific actions.
    The idea is to create urgency for something like, say, a product out of stock. This will generate a greater immediate response from prospects, provided it is used properly.

  5. Emotion

    It is scientifically proven that emotions generate more lucid memories. Obviously, we want to generate positive emotions in our contacts, right?
    If your email generates positive emotions, your user will stay with that offer or that content for a longer time. In addition, their learning process becomes milder.

    Start by inducing that experience through the title.

We come to the important thing. How do we craft an effective subject line?

Next, I am going to list a series of good practices to write a good subject line that increases the efficiency of your emails.

  • Synthesize

    One of the main and most important keys is knowing how to efficiently say what you want to show the user. You have to write in such a way that the user understands it perfectly and also shows an interest. Do not extend too much, be precise and clear in your message.

  • Correct length

    The answer to this question will depend on many factors such as the platform used or the device.
    If the subject is very long, there is a good chance that it will be cut off at some point. On the contrary, if it is too short, it is difficult to elaborate the idea that you want to convey.

    It is, therefore, about reaching an intermediate point in which you are able to express the content of the email in a clear and effective way.

  • Use keywords

    Including important words related to the theme of the campaign ensures that they are read on any device and situation and will increase the reader's predisposition to open it since they already know what the email is about. It is best to add them at the beginning so that they can be grasped by the user as quickly as possible.
    On the contrary, try to avoid accessory words that do not add value and take up space such as "Goodbye" and other types of greetings that you can include in the body of the email.
    In addition, the use of keywords makes it easier to search for emails for those users who use word filters.

  • Arouse curiosity

    You already know that a good magician never reveals his tricks and in this case, the main idea should not be shown in the subject, but you should encourage him to discover it once he opens the mail. That is, if you reveal everything in the matter, interest is lost. Leave him wanting more.

  • Tone

    It is very important that you know your prospects and adapt the tone when addressing them.
    Collect as much information about it and try to find a voice with which they feel identified and comfortable when receiving your emails.

  • A/B testing

    As I always say, your own experience is what will best help you optimize your email marketing campaigns. Try different subject lines and see for yourself what works best. As simple as that.

Things to avoid in your subject lines

It is just as important to know the good practices that can lead you to success, as it is to avoid those that can weigh down the results of your cold email campaigns.

  • Avoid clickbait

    Although the topic should generate interest, it should not be misleading. Generating misleading content can be a good short-term tactic to get clicks, but in the long term it will lead to a loss of interest from the same users. Not to mention that it is the best way to end up in users' spam folders in the medium term.

  • Forbidden words or taboos

    Mentioning certain words can prevent us from passing the spam filter of our prospects' inboxes and our mail cannot be viewed correctly by the user to whom we have sent it.
    These are usually terms related to money or financial entities, medicines, prizes, sexual content, etc. You should inform yourself about it before sending the next email, if you have any doubts about it.

Types of subject lines

There are different types of subject lines that we can use, depending on the purpose and use that we are going to give to the email. There are many more types but you can use the following for reference.


It is about that, with a simple glance, the subscriber knows the relevant information about the content.
“New store opening near you”


Building urgency is a good way to increase opens.
“Only available for the next two days: download this ebook”


Personalization always offers good results, as it generates trust in the recipient.
“Pablo, we have a series that might interest you”

Lists and numbers

Lists have been very popular content in recent years for a reason: they are hard not to read.
“15 things you need to know to write a good email subject line”


Another effective approach is to use question marks to prompt the reader.
“Do you know how to get more clients thanks to email marketing?”

"How to do"

How-tos also tend to attract curiosity very effectively.
“How to create a good email subject line”


Above all, in the case of sales of a physical product, announcing its shortage is synonymous with success.
“iPhone 12: Only 2 units left”


Although always with care, a more controversial tone can work, depending on the audience you are addressing.
“Why do you always make the same mistake”


An imperative tone (always used carefully and without going overboard) can work well by directly asking the subscriber to take action.
“Come to our forum”


The use of statistics and percentages can have good results, especially in educational and informative content.
“We offer you a reason to use “x”: 99.9% recommend it”

First glance

A "first look" at devices or other types of content that interest the reader will undoubtedly arouse their curiosity.
“Meet the new…”


It stands for Fear Of Missing Out. Playing with this psychological factor also usually works.
“Are you going to miss our…?”

Subject line templates

To finish, here are some subject line templates, whose effectiveness has been more than proven over all these years on our cold mail platform.

  1. A question about [target].
  2. [Common acquaintance] has recommended that I get in touch.
  3. Our next steps.
  4. Do not open this email.
  5. X options to start.
  6. Hello [name], [question]?
  7. Should I stay or should I go?
  8. Did you know this about [issue of interest]?
  9. Did you get what you were looking for?
  10. I hope to be of help.
  11. A [benefit] for [your prospect's company].
  12. X tips/idea for [pain point].
  13. Where is the love?
  14. You are not alone.
  15. Do I have permission to close your file?
  16. Cold? Like the fat babies?
  17. Idea for [a topic your prospect is interested in].
  18. 10x [your prospect's company] traction in 10 minutes.
  19. I have found you through [a common contact].
  20. In case you change your mind about partnering with [your company]
  21. 10 minutes — [a date].
  22. We have a [insert fact] in common…
  23. A 3-step plan for your busy week.
  24. [Prospect Name], I think you will like these blogs…
  25. Nice to connect, [prospect name]!
  26. Do you feel [insert an emotion]? Let me help you
  27. 3 weekend ideas for you.

As always, the use of each of these strategies must be considered based on the objectives of your email marketing campaigns, the characteristics of your target audience and your own experience. This is just a base so that, from here, you can develop your own methodology and optimize your own subject lines, in search of the maximum percentage of email openings. Good luck!