For email campaigns to have excellent open rates, they not only have to be enticing but also inviting. In case you're wondering why the open rates are incredibly low, subject lines are the culprit.

Without a good subject line, the recipients won't open the emails so that they won't follow the CTA button, nor purchase. It could also be the end of the business-customer relationship. On the bright side, such a problem is easy to fix.

Below you will find the best formulas that you can use in all situations such as a subject line for follow up email.

1. Ask a question

Even in everyday life, questions get the conversations going. You can use questions to get the recipients to think about their own life and how the email relates to them individually. Take a look at this:

Such a strategy not only gets you to think about the related topic but also it makes the subscribers believe that Apple cares about its plans.

This perception plays a vital role in encouraging brand emotions. Once a brand makes you believe that they care about your particular needs, a natural connection is beginning to form. This is what a study has found:

Therefore, if you don't have inspiration for a subject line, you should always fall back on the safest formula.

Furthermore, asking questions can also work as a follow-up email subject line. If a subscriber hasn't engaged with your campaigns for a while, you can use the subject line as an opportunity to ask questions such as:

• "Are you still following us?"

• "How can we improve?"

• "What can we do for you?"

Such questions don't put the recipient in an awkward position, and they're engaging enough for the subscriber to open the email. If you're stuck on a subject for follow up email, you should take a look at this article.

2. Teach "how-to" something

If you've over-used the question line, you should try the next formula. The majority of your subscribers will engage with information that is new to them.

For example, you should start the email with "How to manage a growing email list." People enjoy solving problems with minimal effort on their behalf. If you let them know how to do something right in the campaign, that means that they don't have to research for themselves.

If you believe that such a subject line doesn't fit with your business, you should take a look at the example below:

You don't have to teach the audience something. You can create subject lines along the lines of:

• "How to save money for the holidays."

• "How to travel smart."

• "How to reach maximum financial potential."

Another great benefit of this formula is that you put yourself in the position of an expert. You know about the industry more than the recipient. Hence, your credibility will increase in front of subscribers.

3. Create a sense of urgency

Not many people like to be rushed into a decision. However, you can use this tactic to your advantage. After all, the majority of people work well when they're under pressure. Such a strategy will encourage the recipients to act fast, so it eliminates the possibility for you to miss an opportunity.

By creating a sense of urgency, you can boost the open rates by up to 14% and the transaction rates by up to 16%. You can see the urgency in this campaign:

However, when it comes to this tactic, you must do it right to make it work. Thus, you shouldn't create a hurry if you intend to give out the same benefit shortly after.

If it isn't right, it will also damage your reputation as you are training the subscribers to wait for a better deal. This will hurt your profits long-term.

4. The big announcement

Another formula that has a high success rate is the announcement line. After all, it doesn't have to be a huge announcement.

You will have the subscribers engaged if you're sending out announcement such as:

Such strategy encourages the subscribers to engage with the email by opening it, following the CTA button, and eventually purchase. Above all, it's also enticing. The word "VIP access" will make people curious to at least open the email.

In the majority of cases, you will put the announcements in the newsletter. That is a great action to take. Nonetheless, you have to be careful about using the word "newsletter" frequently. Eventually, people will get bored of reading such content.

Present the information in an exciting way that will get the attention of your recipients.

5. Don't you love surprises?

Even though a small percentage of the population don't love surprises, it inevitably gets their attention.

By giving your subscribers something unexpected, you will make them believe that you value their presence and you care about them. Take a look at how you can present it:

Of course, this doesn't mean that you have to go out of your way. You can give something away, such as:

• Discount code

• Digital download

• Free entry to a competition

After all, it's known that subject lines that have the word "free" increase the open rates by 10%. By doing something in favor of the subscriber, the action could be returned.

6. Personalize the message

Follow up email subject lines are more effective if they are direct to a specific recipient. The message included should be written for a particular group in the email list, such as, the ones that haven't engaged with you.

The click-through rates can improve by 20%, and the purchase rate increases up to 6x. Fortunately, there aren't many ways that you can mess it up. As long as the subject line speaks directly to the need of the subscribers. Create something similar to this:

As you can see, the information is relevant, and the word choice suits the needs of the subscriber. The word "your" makes it personal, and the content includes information that is useful to the subscriber itself.

7. Curiosity gets the mind thinking

A spark of curiosity here and there never hurt anyone, right? This is why Professor George Loewenstein has come up with the curiosity gap theory. This psychological theory describes the gap between what we know and what we want to know. Once you believe that there's a gap in your knowledge, you feel deprived of information. Hence, you will go out of your way to look for the missing data.

Nonetheless, you have to remember that curiosity doesn't rise if there's no knowledge about the subject at all. So, you have to think about the right topic to link to your campaign. This is what the statistic says:

Once the audience is intrigued with the information, they will want to open the email and find out more information. However, it's also important to remember that you shouldn't rely on this formula too often as it can be perceived as "click-bait." That will annoy the subscribers, and your campaigns can end up in the spam folder.

8. Numbers don't lie

Factual information will increase credibility, and the audience can perceive you as a reliable source of information. This excellent formula has the potential to increase the open rates by up to 2.5%, and it also encourages the recipients to engage with you.

The good news is that you can combine this tactic with email personalization. Groupon has found the perfect combination:

The few words will invite the subscriber to open the email as it helps them to save something. The message is personalized because it's about specific products the recipient has been interested in.

Conclusion on subject lines formulas

All in all, it's essential to entice the reader to go further than just reading the subject line. Furthermore, the content within the campaign should persuade them to follow the CTA button. Fortunately, there are numerous tactics that you can use. However, you shouldn't assume that something is working if you haven't tested it. Use A/B testing and analyze the information.