Bold Red X

The Ultimate Guide to Improving Your Cold Email Subject Lines: Maximize Open Rates

Cartoon woman opening a cold email

Subject lines play a crucial role when it comes to cold emailing. You can consider it a first impression and, for sure, you want to make a strong one when reaching out to prospects for the first time. Even if your content or product is unique, it’ll remain unnoticed unless the recipient opens and reads the email. 

In Bold Red X, we’ve explored numerous combinations of subject lines. However, there’s no universal ‘best’ subject line. It takes a lot of testing because what works today might not work tomorrow. 

Today, we will focus on how to optimize subject lines in cold emails to achieve a higher open rate and eventually, a higher conversion rate. We would like to share with you a summary of our testing and experimenting in this area.

Know your prospects:

In order to craft an effective subject line, it’s really important to know who you’re reaching out to. You also want to avoid using misleading subject lines. Put yourself in your prospect’s position and think about what they would find appealing.

For instance, if you’re contacting a CEO or a company founder, it might be smart to mention something positive about their company in the subject line. On the other hand, a regular engineer might be pleased to see a subject line referring to a feature they worked on in a project. It’s all about doing your research and understanding your target audience.


The subject lines that yield the best results for us are the personalized ones. Adding the recipient’s name is particularly effective as it distinguishes the email from regular spam.

For example, when contacting a content marketer or a VP of marketing, you can use something similar to the following:

Hey (name), really enjoyed your recent post on (topic)

Another example when reaching out to a CEO:

Hey (name), congrats on the successful fund round!

These personalized subject lines often generate high open rates because they showcase that you have done your homework and conducted research. It demonstrates a genuine effort on your part.

Don't be generic:

We have conducted various tests on different subject lines and we can say that generic or email newsletter-sounding subject lines are the ones that perform poorly and result in low open rates.

An example of this: 

Working together with (company)

This subject line lacks personalization and seems spammy. So, it’ll accordingly lead to lower open rates.

Another example:

Best deal for (company)

Similarly, this subject line doesn’t perform well. It gives the impression of a typical e-commerce email newsletter that people often never open. 

Avoid using such generic subject lines and strive for more engagement and personalization to increase open rates.

Avoid misleading subject lines:

It’s essential to use subject lines that get your prospect’s attention and get them to open your emails. However, you want them to open with genuine interest and not just because of your attractive subject line. That’s why the content of your email holds great significance as well. Avoid long sales templates and keep your email concise and straightforward instead. Stay away from generic sales templates as much as you can.

Here are some examples of subject lines that might generate high open rates but result in low response rates:


Such subject lines result in an exceptionally low response rate. And yes, we’ve received a lot of emails with similar subject lines only to find lengthy sales templates promoting SEO services. I’m sure many of you have encountered similar emails. 

Another example:

Hey (name), must read!

While this subject line might have a chance of being opened, it doesn’t necessarily lead to responses or conversions especially if you’re selling something. The prospect might even end up feeling more frustrated than compelled to make a purchase. 

To maximize engagement and response rates, shift your focus to subject lines that accurately reflect the content of your email and foster genuine interest and trust from your prospect.

Include introductions:

The subject lines that achieve the highest conversion rates are the ones that include introductions with names. Incorporating two names in a subject line almost always guarantees an open (assuming you have high-quality leads).

For instance:

Came across (company) through (name)

This approach works exceptionally well, however, it does require some time for personal research. The best way to apply this is to use LinkedIn. Look for a mutual connection and include that person’s name in the subject line. Ideally, it’s best to ask the person for a direct introduction, but if you’re sending 50+ cold emails a day, you may not have the time for it. In such cases, quickly browse through LinkedIn to identify any shared connections and create a personalized subject line based on that information for your cold email.

The content that follows this subject line is important. In the email, you might want to include a line such as “Hey, while browsing LinkedIn, I noticed that we have a mutual connection with (name). We went to college together!” to establish the context of the introduction.

Quality of leads:

Regardless of the subject line used in your cold emails, it’s crucial to have quality leads and accurate information. Even if you send 500+ emails with personalized subject lines, it won’t give you the results that you want if the lead information is incorrect.

It’s essential to focus on high-quality leads. Ask yourself whether the person matches your ideal buying profile. Is this person likely to recognize your service or products as something they need or desire right away? 

Ensuring that your leads are a good fit for your offerings greatly increases your chances of success. 

Unlock Your Cold Email Success: Optimizing Subject Lines for Maximum Impact

By following the strategies and insights outlined in this ultimate guide, you can optimize your cold email subject lines, maximize open rates, and ultimately increase your chances of converting prospects into customers. Remember, subject lines are just the first step towards building meaningful connections and driving successful email outreach campaigns.