Cold Email A/B Testing to Boost Open & Reply Rate [2024 Guide]

Created On:
April 3, 2023
Updated On:
May 14, 2024
Cold Email A/B Testing

Truth be told, it's very hard to create a successful cold email campaign, especially if you are just starting out. It's even harder to understand what works in cold emails and what does not. 

And what can be better than some good old trial-and-error method, right? 

That's where cold email A/B testing comes in. Split testing or A/B testing is the most effective way to identify what works for your cold email campaigns and what doesn't. 

In this blog post, you will learn cool A/B testing hacks to maximize your cold email campaign's reply rate, CTR, and, most importantly, conversions. So, get ready to ramp up your ROI

Here we go.

What is A/B Testing? 

Split testing, also known as A/B testing, is an experimental method of testing at least two or more versions of a variable (cold emails, page element, web pages, etc.) at the same time to decide which version of the variable drives more business metrics such as sales number and leaves a maximum direct impact.

For instance, if you are a cold email marketer, you can split test two email versions of an email copy, subject lines, personalized first lines, CTAs, images, or the entire email sequence if needed. 

How to Perform A/B Testing with Cold Emails? [Step-by-Step Process]

Before you jump into A/B testing your cold emails, here are some email a/b testing best practices to keep in mind: 

#Test only one aspect of a cold email at once; for instance, test personalized first lines only to get a clear picture of the metrics. 

#Measure all the cold email KPIs – e.g., email open rates, response rates, click rates, etc. to understand if any of the variations live up to your set KPI standards. 

#Run your cold email split test through a big-enough email list of prospects, ideally around 200 people, to gain relevant insights. 

Let’s get started.

Step 1: Subscribe for a Cold Email Tool 

Choose a cold email tool that can accommodate sending 1000s of emails without affecting deliverability. Along with A/B testing feature, the tool has features like

  • Warm-up
  • Automated follow-ups
  • Auto-mailbox rotation
  • Multi-channel outreach
  • Master inbox
  • API Access
  • Unlimited Seats
  • Webhooks & Integrations

Step 2: Set Up Your Account 

Create an account on the outreach tool's site before you begin sending cold emails. Once that is done, connect the tool to your email service provider (ESP).

Make sure you set up SPF, DKIM, DMARC, and MX records. This will also improve the overall security and credibility of your email messages. 

Warm Up

Prior to starting a campaign or sending out bulk emails, it is essential to warm up  your email account. Warm it up gradually over a two-week period.

Create the Email Campaign

Find the "add campaign" button in the software and click on it. 

Import your Email List

Make sure your email list is segmented and organized before adding it to the cold email tool. The lead list needs to be in csv format, similar to the file below. 

Write the Subject

Create a short, attention-grabbing subject line for the cold email campaign. 

Write the Email Body

Write the email content—a catchy opening line, email body, and CTA. For ready made cold email templates, go there

Step 3: Set Up A/B Test

In the cold email tool, look for the A/B testing option. It might be beside or below the campaign settings.

You can do A/B testing on Smartlead by creating variants. 

Select "add variant" from the menu as shown in the below image.

If you want to test just the subject lines, you can keep the email content the same. But to test opening lines, CTA, or email body,  you need to create a different version of the same email in the next variant (variant 2).

Once you've finished creating the email variations, click "save & next" to finish. Prior to scheduling the emails, double-check. Consider the recipient's time zones when scheduling the emails. 

Step 4: Monitor Performance Metrics

Keep an eye on the KPIs like response rates, click-through rates, and open rates. Real-time data should be available on the analytics dashboard of the cold email tool.

Compare how well the two email variations have performed. Identify which one has better reply rates and click-through rates.

Study why one email variant has outperformed the other and use that knowledge to improve your cold email campaigns. 

What are the Benefits of Cold Email A/B Testing? 

You can identify the elements of success and minor touch-points that can improve engagement through A/B testing your cold email campaigns. Here are a few of the key benefits of A/B testing for cold sales emails: 

Improve Email Open Rates

A/B testing helps you determine the best-performing personalized subject lines that are more likely to entice your prospective customers to open your emails. As preview text in emails can be a major driving point for opening an email, you can split-test different preview texts to improve email open rates significantly.

Increase Click-Through Rates

Split testing helps email marketers identify the most effective CTAs and email copies to drive more clicks. In fact, a study by Campaign Monitor found that segmented cold email campaigns (which can be created using A/B testing) have a 14.32% higher click-through rate than non-segmented campaigns.

Boost Conversion Rates

A/B testing can help businesses optimize their cold emails for conversions by testing different crucial elements such as email copy, images, and CTAs. By testing different variations of these elements, businesses can determine which ones generate the highest conversion rates and optimize their email campaigns accordingly.

Higher Cost-Effectiveness

Split testing helps businesses cut budget costs significantly by identifying the highest-performing elements of respective email campaigns. This way, businesses can avoid spending unnecessary resources on a less effective cold email strategy and lower cost per conversion ratio. 

Reduce Bounce Rates

A/B testing helps businesses implement the most effective email-sending practices; thus, it helps increase email deliverability rates. This way, you can reduce your cold email campaign's bounce rates by testing different email subject lines and email sending schedules to avoid triggering spam filters and increase the chances of the email being delivered to the recipient's inbox.

Cold Email A/B Testing Methods

There are two different types of split testing for cod emails: 

Classic A/B Testing 

The classic A/B testing methodology requires comparing two or more visions of the same cold email. For example, the classic split test can check which version of a call-to-action gets more click-through rate. 

Multivariate A/B Testing

An advanced split testing methodology, multivariate A/B testing can analyze more than one email element change in a cold email. For example, you can check which first line, CTA, or image works best within one test without running an A/B test for each of the variables. 

Variables to A/B Test in Cold Email Campaigns

Variables to A/B test in cold emails campaigns

The first thing you have to do is determine your goal for the particular cold email campaign before you test different variables in a cold email. Ask yourself whether you want to increase the email open rates or reduce bounce rates. Let's take a look at each of the testing variables.

For Improving Cold Email Open Rates

1. Test the Subject Line

The subject line is the first thing your prospects notice to decide whether they want to open an email or not. No matter how brilliant your email copy is, the subject line determines email open rates. 

For example, you can test subject lines based on the following: 

  • Long vs. short subject lines
  • Statement vs. question
  • Generic subject line vs. personalized subject line

On that note, personalized subject lines get 39.69% of email opens and email click rates, which is almost double the non-personalized ones. 

2. Test Different Preview texts

Preview text, also known as preheader text, is a brief outline of the email just below a subject line. Besides subject lines, preheader texts also impact email open rates. So, it is important to test a few preheader texts to find out the most enticing one for your cold email outreach. 

For Higher Reply Rates for Cold Emails

1. Email Text or Email Body 

A higher email open rate doesn't mean more replies, let alone conversions. It's possible your prospects are opening your emails and doesn't find the email content enticing enough to reply. That's why testing the email copy is essential to grab your prospects' attention and convince your prospects to reply. 

2. Unclear/Vague CTA

Lack of clarity in your CTA can lower reply rates (and even click-through rates) significantly. To identify with your potential customers' triggers and what CTA works best, we'd recommend you A/B test different cold email versions and CTA. 

Want to learn how to write an enticing cold email? Read here

A/B Testing Ideas for Subject Lines

Sure, there are a few guidelines you must follow while writing a cold email subject line, or else your emails might land in the spam folder. However, following the CAN-SPAM act and GDPR regulations, here are a few subject line A/B testing ideas: 

1. 60 Characters or Nine words 

A Mailchimp study has shown that subject lines within nine words, or 60 characters work best for cold sales emails. However, this is not the case for all kinds of cold email campaigns, as longer subject lines give a better understanding of the email. 

So, it's best if you test a few options to find out what works for your campaigns. 

2. Lowercase Letters 

Most people capitalize the first letter of each word in the subject lines. However, many marketing experts suggest that it doesn't generate good results for many businesses. A/B test your subject lines with sentence cases and other formats to see what your prospects like. 

3. Personalization

Create two variations for the subject line – one with prospects' names and their company names and another version without it. Check which one gets more email opens and replies to choose the right one. 

With a powerful tool such as Smartlead, you can personalize your cold email subject lines at scale with prospect data. 

4. Emoji or No Emoji

As the younger generations are getting into B2B space, emojis can be a good option to catch your recipients' attention. Although the use of emojis is getting more and more popular, it doesn't work for some industries. So, test subject lines with and without emojis to check what works best for you.  

A/B Testing Ideas for Email Copy

A/B testing is a must to check which variation of an email copy generates more response rates. Here are some ideas: 

1. Formal Greetings Vs. Non-Formal Greetings

Greetings are the first thing one reads after opening an email. You can set a casual tone with "Hi," "Hello," or "Hey," which is less formal. Also, you can start with a formal "Hello" or "Dear {first name}" in your emails. Make sure you split-test both options to set the right tone for your email campaigns. 

2. Intro Vs. No Intro 

Sales professionals usually don't add an intro of the sender in the first line of the cold email. However, it might be good for more formal B2B industries. Find out what works for you by split-testing both variations.  

3. Use of Images, GIFs, and Videos Vs. Plain Text

Visuals make emails more interesting and increase customer engagement. But the image-heavy email format might not work all the time. Test your emails to check whether visual-heavy emails or plain text emails work more effectively. 

4. Generic Personalization Vs. Hyper-Personalization

Test whether simple customization in the initial email generates the desired result. You can test follow-up emails with hyper-personalization in the same email sequence to generate more conversions or not. This will save you from hyper-personalizing the entire email sequence, and you can do it only when it's necessary. 

Check out the money-making cold email templates that will skyrocket your business's ROI. 

A/B Testing Ideas for CTAs

You must split-test your CTA to maximize your conversion rates. It is very important to find out the right implementation of the CTA to drive sales. 

Here are some ideas to A/B test your CTAs: 

  • Placement of the CTA
  • Plain text Vs. formatting text
  • Proposing a time for a meeting Vs. offering a calendar link

A/B Test for Email Sending Schedule

A Yesware study has shown that Monday, followed by Tuesday and Wednesday, see the maximum number of email opens. The same study also suggests that the best time of day to send emails is between 1-4 pm. 

These stats can be pretty decisive, as the best time and day to receive sales emails might vary based on the demographics and time zone of your audience base. So, research your prospects and acquired demographic data, and A/B test your emails to find the best time to send cold emails to your prospects for higher email open and reply rates. 

Cold Email A/B Testing Best Practices

To launch effective cold email marketing campaigns, keep the following tips in mind: 

  • Split test each and every aspect separately. If you want to speed up the process, try more than three variations at once but don't go beyond four at one go. 
  • Make sure you are testing the right variations for appropriate KPIs. Otherwise, it will just be a waste of time. 
  • While split testing, make sure you are comparing two variations only when the conditions are the same. For example, you can't compare the reply rate for an email you sent on Tuesday with that you sent on Friday. 
  • The whole point of A/B testing cold emails is to make informed and data-backed decisions. So, keep an eye on the split testing data. 

Use Smartlead: A/B Test to Maximize Business ROI

With Smartlead, the amazing email marketing software, sales reps can: 

  • Create unlimited sender accounts (email address) to reach a wider audience base. 
  • Personalize your email messages with its AI personalization and with attributes like prospect's name, job role, company name, etc., at scale. 
  • Maintain an excellent sender reputation with automated email warmups. 
  • Set up custom conditional email-sending triggers.
  • Manage all your emails in the master mailbox without complex email routing.
  • Personalize your follow-up email sequences. 

So, what are you waiting for? Start your 14-day free trial at Smartlead; no credit cards are required. 


What Elements of a Cold Email Should You A/B Test?

You can A/B test various elements of a cold email to optimize its performance. Common elements to test include subject lines, email copy, sender's name, call-to-action (CTA) buttons, images, and email timing. Experimenting with these elements helps identify what resonates best with your audience and improves open rates, click-through rates, and overall engagement.

How Many Recipients Do You Need for Effective A/B Testing?

The number of recipients needed for effective A/B testing can vary depending on the desired level of statistical significance and the size of the anticipated impact. Generally, it's recommended to have a minimum of a few thousand recipients per variant to obtain meaningful results. However, larger sample sizes often yield more reliable insights. It's essential to consider factors like the expected conversion rate and the desired level of confidence when determining the appropriate recipient size for your A/B tests.

Can A/B Testing Improve Email Open and Response Rates?

Yes, A/B testing can improve email open and response rates. It involves sending two variations of an email (A and B) to a subset of your audience to determine which performs better. By testing different elements like subject lines, email copy, images, or CTAs, you can identify what resonates most with your audience. This data-driven approach allows you to refine your emails, increasing the likelihood of higher open rates, better engagement, and improved overall email marketing effectiveness.

How Long Should You Run an A/B Test on Cold Emails?

A/B testing duration for cold emails can vary, but it's generally advisable to run the test for at least one to two weeks. This timeframe allows you to collect sufficient data and observe patterns in recipient behavior. However, the ideal duration may depend on your email volume and specific goals. Ensure your sample size is statistically significant, and monitor key metrics like open rates and click-through rates to make informed decisions about the winning variation.

What Are Common Mistakes in Cold Email A/B Testing?

One common mistake is not testing a significant change. Small tweaks may not yield noticeable results. Another error is not giving the test enough time to gather sufficient data. Rushed decisions can lead to inaccurate conclusions. Additionally, ignoring the importance of a sizable sample size can skew results. Lastly, failing to track and analyze metrics effectively can hinder your ability to learn from the A/B test and make informed adjustments.

How Do You Interpret Results from Cold Email A/B Testing?

Interpreting results from cold email A/B testing involves analyzing key metrics such as open rates, click-through rates, and conversion rates for the different variations of your email. Compare the performance of the variations and identify which one outperforms the others. Look for patterns and insights in the data, and use this information to refine your email content and strategy. Keep in mind that A/B testing is an ongoing process, and continuous iteration based on results is essential for optimizing your cold email campaigns.

What’s a Rich Text element?

The rich text element allows you to create and format headings, paragraphs, blockquotes, images, and video all in one place instead of having to add and format them individually. Just double-click and easily create content.

  • dfbvrsg
  • svsv

Static and dynamic content editing

A rich text element can be used with static or dynamic content. For static content, just drop it into any page and begin editing. For dynamic content, add a rich text field to any collection and then connect a rich text element to that field in the settings panel. Voila!

How to customize formatting for each rich text

Headings, paragraphs, blockquotes, figures, images, and figure captions can all be styled after a class is added to the rich text element using the "When inside of" nested selector system.

Author’s Details

Rajnish Das

Rajnish Das is an in-house writer at SmartWriter and SmartLead. She writes product-oriented, data-driven content for B2B SaaS audiences and educates them on marketing and sales topics. Her expertise includes outbound marketing techniques like cold emailing and LinkedIn outreach.


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Frequently asked questions

General Questions

What is Smartlead's cold email outreach software?

Email automation FAQs- Smartlead

Smartlead's cold email outreach tool helps businesses scale their outreach efforts seamlessly. With unlimited mailboxes, fully automated email warmup functionality, a multi-channel infrastructure, and a user-friendly unibox, it empowers users to manage their entire revenue cycle in one place. Whether you're looking to streamline cold email campaigns with automated email warmups, personalization fields, automated mailbox rotation, easy integrations, and spintax, improve productivity, or enhance scalability with subsequences based on lead’s intentions, automated replies, and full white-label experience, our cold email tool implifies it in a single solution.

What is Smartlead, and how can it enhance my cold email campaigns?

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Smartlead is a robust cold emailing software designed to transform cold emails into reliable revenue streams. Trusted by over 31,000 businesses, Smartlead excels in email deliverability, lead generation, cold email automation, and sales outreach. A unified master inbox streamlines communication management, while built-in email verification reduces bounce rates.
Additionally, Smartlead offers essential tools such as CNAME, SPF Checker, DMARC Checker, Email Verifier, Blacklist Check Tool, and Email Bounce Rate Calculator for optimizing email performance. 

How does the "unlimited mailboxes" feature benefit me?

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Our "unlimited mailboxes" feature allows you to expand your email communications without restrictions imposed by a mailbox limit. This means you won't be constrained by artificial caps on the number of mailboxes you can connect and use. This feature makes Smartlead the best cold email software and empowers you to reach a wider audience, engage with more potential customers, and manage diverse email campaigns effectively.

How does Smartlead as a cold emailing tool can automate the cold email process?

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Smartlead’s robust cold email API and automation infrastructure streamline outbound communication by transforming the campaign creation and management processes. It seamlessly integrates data across software systems using APIs and webhooks, adjusts settings, and leverages AI for personalised content.

The cold emailing tool categorises lead intent, offers comprehensive email management with automated notifications, and integrates smoothly with CRMs like Zapier, Make, N8N, HubSpot, Salesforce, and Pipedrive. Smartlead supports scalable outreach by rapidly adding mailboxes and drip-feeding leads into active campaigns Sign Up Now!

What do you mean by "unibox to handle your entire revenue cycle"?

Email automation FAQs- Smartlead

The "unibox" is one of the unique features of Smartlead cold email outreach tool, and it's a game-changer when it comes to managing your revenue cycle. The master inbox or the unibox consolidates all your outreach channels, responses, sales follow-ups, and conversions into one centralized, user-friendly mailbox.

With the "unibox," you gain the ability to:
1. Focus on closing deals: You can now say goodbye to the hassle of logging into multiple mailboxes to search for replies. The "unibox" streamlines your sales communication, allowing you to focus on what matters most—closing deals.

2. Centralized lead management: All your leads are managed from one central location, simplifying lead tracking and response management. This ensures you take advantage of every opportunity and efficiently engage with your prospects.

3. Maintain context: The "unibox" provides a 360-degree view of all your customer messages, allowing you to maintain context and deliver more personalized and effective responses.

How does Smartlead ensure my emails don't land in the spam folder?

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Smartlead, the best cold email marketing tool, ensures your emails reach the intended recipients' primary inbox rather than the spam folder. 

Here's how it works:
1. Our "unlimited warmups" feature is designed to build and maintain a healthy sending reputation for your cold email outreach. Instead of sending a large volume of emails all at once, which can trigger spam filters, we gradually ramp up your sending volume. This gradual approach, combined with positive email interactions, helps boost your email deliverability rates.

2. We deploy high-deliverability IP servers specific to each campaign. 

3. The ‘Warmup’ feature replicates humanized email sending patterns, spintax, and smart replies.
4. By establishing a positive sender reputation and gradually increasing the number of sent emails, Smartlead minimizes the risk of your emails being flagged as spam. This way, you can be confident that your messages will consistently land in the primary inbox, increasing the likelihood of engagement and successful communication with your recipients.

Can Smartlead help improve my email deliverability rates?

Email automation FAQs- Smartlead

Yes, our cold emailing software is designed to significantly improve your email deliverability rates. It enhances email deliverability through AI-powered email warmups across providers, unique IP rotating for each campaign, and dynamic ESP matching.
Real-time AI learning refines strategies based on performance, optimizing deliverability without manual adjustments. Smartlead's advanced features and strategies are designed to improve email deliverability rates, making it a robust choice for enhancing cold email campaign success.

What features does Smartlead offer for cold email personalisation?

Email automation FAQs- Smartlead

Smartlead enhances cold email personalisation through advanced AI-driven capabilities and strategic integrations. Partnered with Clay, The cold remaining software facilitates efficient lead list building, enrichment from over 50 data providers, and real-time scraping for precise targeting. Hyper-personalised cold emails crafted in Clay seamlessly integrate with Smartlead campaigns.

Moreover, Smartlead employs humanised, natural email interactions and smart replies to boost engagement and response rates. Additionally, the SmartAI Bot creates persona-specific, high-converting sales copy. Also you can create persona-specific, high-converting sales copy using SmartAI Bot. You can train the AI bot to achieve 100% categorisation accuracy, optimising engagement and conversion rates.

Can I integrate Smartlead with other tools I'm using?

Email automation FAQs- Smartlead

Certainly, Smartlead cold email tool is designed for seamless integration with a wide range of tools and platforms. Smartlead offers integration with HubSpot, Salesforce, Pipedrive, Clay, Listkit, and more. You can leverage webhooks and APIs to integrate the tools you use. Try Now!

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Is Smartlead suitable for both small businesses and large enterprises?

Smartlead accommodates both small businesses and large enterprises with flexible pricing and comprehensive features. The Basic Plan at $39/month suits small businesses and solopreneurs, offering 2000 active leads and 6000 monthly emails, alongside essential tools like unlimited email warm-up and detailed analytics.

Marketers and growing businesses benefit from the Pro Plan ($94/month), with 30000 active leads and 150000 monthly emails, plus a custom CRM and active support. Lead generation agencies and large enterprises can opt for the Custom Plan ($174/month), providing up to 12 million active lead credits and 60 million emails, with advanced CRM integration and customisation options.

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What type of businesses sees the most success with Smartlead?

No, there are no limitations on the number of channels you can utilize with Smartlead. Our cold email tool offers a multi-channel infrastructure designed to be limitless, allowing you to reach potential customers through multiple avenues without constraints.

This flexibility empowers you to diversify your cold email outreach efforts, connect with your audience through various communication channels, and increase your chances of conversion. Whether email, social media, SMS, or other communication methods, Smartlead's multi-channel capabilities ensure you can choose the channels that best align with your outreach strategy and business goals. This way, you can engage with your prospects effectively and maximize the impact of your email outreach.

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How can Smartlead integrate with my existing CRM and other tools?

Smartlead is the cold emailing tool that facilitates seamless integration with existing CRM systems and other tools through robust webhook and API infrastructure. This setup ensures real-time data synchronisation and automated processes without manual intervention. Integration platforms like Zapier, Make, and N8N enable effortless data exchange between Smartlead and various applications, supporting tasks such as lead information syncing and campaign status updates. Additionally, it offers native integrations with major CRM platforms like HubSpot, Salesforce, and Pipedrive, enhancing overall lead management capabilities and workflow efficiency. Try Now!

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Do you provide me with lead sources?

No. Smartlead distinguishes itself from other cold email outreach software by focusing on limitless scalability and seamless integration. While many similar tools restrict your outreach capabilities, Smartlead offers a different approach.

Here's what makes us uniquely the best cold email software:

1. Unlimited Mailboxes: In contrast to platforms that limit mailbox usage, Smartlead provides unlimited mailboxes. This means you can expand your outreach without any arbitrary constraints.

2. Unique IP Servers: Smartlead offers unique IP servers for every campaign it sends out. 

3. Sender Reputation Protection: Smartlead protects your sender reputation by auto-moving emails from spam folders to the primary inbox. This tool uses unique identifiers to cloak all warmup emails from being recognized by automation parsers. 

4. Automated Warmup: Smartlead’s warmup functionality enhances your sender reputation and improves email deliverability by maintaining humanised email sending patterns and ramping up the sending volume. 

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How secure is my data with Smartlead?

Ensuring the security of your data is Smartlead's utmost priority. We implement robust encryption methods and stringent security measures to guarantee the continuous protection of your information. Your data's safety is paramount to us, and we are always dedicated to upholding the highest standards of security.

How can I get started with Smartlead?

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Getting started with Smartlead is straightforward! Just head over to our sign-up page and follow our easy step-by-step guide. If you ever have any questions or need assistance, our round-the-clock support team is ready to help, standing by to provide you with any assistance you may require. Sign Up Now!

How can I reach the Smartlead team?

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We're here to assist you! You can easily get in touch with our dedicated support team on chat. We strive to provide a response within 24 hours to address any inquiries or concerns you may have. You can also reach out to us at

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