8 Best Email Marketing Software for A/B Testing in 2026

Any e-mail marketer has launched a campaign and then seen the poor open rate return, wondering where it all went wrong: the subject line, timing of sending, preview text… A/B testing provides the answer to this question based on hard data rather than pure speculation. However, not all testing solutions perform equally, and some even fail miserably. For example, they require costly accounts or provide limited functionality for testing.

In total, eight A/B testing platforms are reviewed here; they are chosen by the value provided in the form of testing capabilities offered. All reviews revolve around four questions: What do A/B tests actually do? Which plan activates this functionality? And, most importantly, what other competitors don’t reveal about their testing solutions?

What Is Email A/B Testing?

A/B testing for emails involves the dispatching of two different emails for comparison to determine which one works better. This usually happens through most testing platforms in relation to subject lines. However, the most efficient platforms go much beyond this by testing the actual email content, the call to action used, the sender name used, the timing of dispatch, and the whole automated sequence.

What to Look for Before You Choose

• Which plan unlocks A/B testing? Many platforms hide this behind mid or premium tiers.

• What can you actually test? Subject lines are baseline. Look for content, send time, and automation-level testing.

• How many variations? Two is standard. Five or more is serious.

• Does it pick a winner automatically? Auto-selection based on statistical confidence saves time and avoids bad decisions on thin data.

• Is there revenue attribution? Open rates are a proxy. Revenue per variant is the real metric.

Quick Comparison

8 Best Email Marketing Software for A/B Testing

1. Mailmodo

Mailmodo is an AI email marketing software that helps you create, automate, and optimize campaigns effortlessly. From planning strategy to writing copy and building journeys, Mailmodo’s AI Agents handle it all, with no technical expertise needed. It’s the fastest way to send smart, interactive, and high-performing emails.

How A/B Testing Works Here

Testing covers subject lines, email content, send times, and template variations. The AI Subject Line Generator creates test variants based on campaign context. The visual Journey Builder supports conditional branching between automation paths, which allows flow-level testing. Click maps feed directly into test design, showing which sections of the email drove engagement before the next test is set up.

What Others Are Not Telling You

Most reviews focus only on Mailmodo’s AMP email capabilities, but its biggest advantage is actually the AI-first workflow. Mailmodo’s AI Agents help generate campaign strategies, write copy, design emails, create audience segments, and optimize journeys from one platform, reducing the need for multiple marketing tools.

Watch Out For

Interactive AMP emails are not supported equally across all email clients. Outlook and Apple Mail users receive HTML fallback versions instead. Advanced AI automations and interactive experiences may also require some initial learning for new users.

Pricing

Best For

Startups, SaaS brands, and marketing teams looking for an AI-first email marketing platform that helps automate campaign creation, email design, segmentation, testing, and customer journeys with minimal manual work.

Review

"There is no doubt that Mailmodo is the best AMP email solution in the market, which allows us to send interactive emails directly to the user. I really love the UI and UX for this platform." — Deepa, IT & Services Professional, Capterra.

2. ActiveCampaign

ActiveCampaign is the strongest platform in this list for teams that want to test beyond individual emails. While every other tool here limits A/B testing to campaign-level sends, ActiveCampaign extends split testing into full automation workflows on the Pro plan.

How A/B Testing Works Here

With Starter Plan customers, up to five versions can be run with regard to the testing of subjects, senders, content, and sending times. The Pro Plan allows users to test entire automated email flows; for example, a four-step welcome sequence can be compared to a three-step sequence, while also testing a nurture email flow based on discounts versus one based on social proof. Predictive Sending automates send time optimization on a per-contact basis.

What Others Are Not Telling You

Each of them describes a Starter package costing $15 per month, while keeping quiet about the necessity to use the Pro package for $79 per month (per 1,000 contacts) to conduct A/B testing on an automation level. That means $205 per month (per 5,000 contacts) or $549 per month (per 25,000 contacts). Yet, the automation testing offered is really the best in this competition.

Watch Out For

The learning curve is substantial. It takes some effort to program branching workflows in automation sequences, while debugging an incorrectly programmed sequence is more difficult compared to other platforms. For smaller companies without a marketing operations specialist, it will take time on the platform before seeing results from A/B testing.

Pricing

Best For

Mid-size B2B companies and SaaS teams that need automation-level split testing and want to compare full customer journeys, not just individual email sends.

Review

"Our customers are feeling like the emails are written JUST to them. Based on the segmentation feature and the way ActiveCampaign breaks down our leads, we are on the road to more sales." — Shira B., CEO, Marketing and Advertising, Capterra.

3. Mailchimp

Mailchimp is where most marketers run their first A/B test. The interface is familiar, the setup takes minutes, and the results page is clear enough to share with a non-technical stakeholder.

How A/B Testing Works Here

All subscription plans come with testing of subject lines, from addresses, content, and sending times, with a limit of three variations tested at once. Multivariate testing comes under the Premium plan that allows testing of combinations of different variables. There is no level of automation for testing.

What Others Are Not Telling You

The number of contacts and emails permitted under the free plan has been reduced to 250 and 500, respectively, as of 2026. The number of emails is not enough to conduct a statistically significant A/B test. Groups looking to use the free plan for conducting such tests would soon bump up against the limit. The limitation of three variants offered on the premium plans is another actual limitation that most of the review sites mention only superficially.

Watch Out For

Mailchimp costs 2-3 times more than Brevo and MailerLite. Companies that have been using Mailchimp for years and that have not updated their evaluation regarding prices will likely be paying too much because of the competitive pricing that is offered by other companies offering the same services.

Pricing

Best For

New marketers and small teams running their first split tests who want a familiar, low-friction setup without needing automation-level testing.

Review

"Mailchimp's split testing feature is a core part of their offering — testing subject lines, sender names, content, and send times — and the reporting makes it easy to act on results immediately." — Denys Velykozhon, Marketing Lead, Mailtrap Blog.

4. Klaviyo

Klaviyo is the default for ecommerce brands that want test results tied directly to revenue. It is not a general-purpose email tool. It is built for B2C businesses with store data who want marketing decisions driven by purchase behavior.

How A/B Testing Works Here

Campaign testing enables users to test multiple variants of at least four types for subject line, message body, time, and sender information on all paid tiers. In-app Flow A/B testing within the automation builder feature enables the whole sequence to be tested via splitting it into two branches, attributing the revenues from each branch accordingly. Welcome flows with the 10 percent discount can be tested against those recommending best sellers.

What Others Are Not Telling You

Active Profile Billing Model at Klaviyo was introduced in February 2026. All contacts in an account – even those who are not engaged anymore – will contribute towards tier limits independent of how frequently they receive emails. Teams who have not done list cleansing recently will end up paying for people they can no longer reach.

Watch Out For

There is no billing discount for an annual subscription. Most of the other platforms provide 15 to 20 percent discount for the annual subscription plan. In case of Klaviyo, there is no difference whether you pay annually or monthly, so the actual cost of ownership would be more.

Pricing

Best For

Ecommerce brands on Shopify, WooCommerce, or BigCommerce that want flow-level A/B testing with purchase revenue attribution and deep store data integration.

Review

"What I like best about Klaviyo is the segmentation and automation possibilities. We can create different flows based on customer actions, behavior, and lifecycle stage, so communication becomes much more relevant." — Tom I., Ecommerce Brand Manager, G2.

5. Brevo

Brevo's main advantage over every other platform in this list has nothing to do with A/B testing features specifically. It charges by email volume, not contact count. A business with 50,000 contacts sending one newsletter per month pays for 50,000 sends, not for 50,000 contacts sitting in the database.

How A/B Testing Works Here

Testing involves subject line and e-mail body on the Starter plan and higher, in a clean set-up involving the size of the test group, winning criteria, and duration. The winner gets selected automatically by the platform. Send time testing can also be done, which is helpful for multi-time zone audiences.

What Others Are Not Telling You

A/B testing at an automation level is not possible in Brevo at all. Tests can only be done on campaign sends individually. Teams looking for options to test nurture campaigns and onboarding campaigns are unlikely to find them with Brevo. Brevo is presented by most reviews as a direct competitor in terms of test capabilities, despite being more limited than ActiveCampaign, Klaviyo, or Omnisend.

Watch Out For

The issue of deliverability has been noted by some users as being inconsistent. In order for the A/B testing to bear fruit, the deliverability should be consistent between the two versions. Should one version end up landing in spam more often than the other, the test will become irrelevant despite the difference in content.

Pricing

Best For

Budget-conscious teams with large contact lists sending at moderate frequency who want predictable monthly costs without per-contact fees.

Review

"Brevo makes email marketing extremely easy to manage, even for teams without a technical background. The drag-and-drop editor is intuitive." — Manuel F., G2.

6. MailerLite

MailerLite includes A/B testing on its free plan. No other platform on this list does the same. That is the single most important thing to know about it in this context.

How A/B Testing Works Here

A free trial plan will provide testing of subject lines and sending times. A $10 monthly plan called the 'Growing Business' plan includes testing of multiple variables in one test, something that most platforms usually do for the top-level account. Testing landing pages is also included

What Others Are Not Telling You

The multivariate test option for $10 per month is really a good one. Other software providers require from $50 to $350 monthly for similar functionality. The pricing factor becomes very critical when there is a budget constraint in the team. Moreover, the landing page test comes in at the same price point.

Watch Out For

Automation-level A/B testing is not available. Full workflow sequences cannot be split-tested, which limits insight for teams that rely heavily on automated nurture flows. Account approval has also been flagged in Capterra reviews as occasionally strict, with some users experiencing unexpected suspensions related to bounce rates or list hygiene, which can be disruptive mid-campaign.

Pricing

Best For

Solopreneurs, bloggers, creators, and early-stage startups that want real A/B testing without a financial commitment, and small teams that need multivariate testing without paying premium prices.

Review

"MailerLite is easy to use and makes it simple to create great-looking email templates. The automation building and easy-to-view analytics genuinely help improve results over time." — Sandra S., Alternative Medicine Practitioner, Capterra.

7. HubSpot Marketing Hub

HubSpot Marketing Hub is the right choice for one specific type of team: those already running HubSpot's CRM who want email A/B testing connected natively to pipeline revenue data. For teams outside that context, the pricing makes it very hard to justify.

How A/B Testing Works Here

A/B Testing for Emails is included in the Professional Package. Testing of two versions will be carried out according to the winning criteria determined by either the open rate, click-through rate, or customized metric. With the CRM integration, the outcome of such tests can be traced to pipeline results, such as what subject line brought more clicks, leading to sales leads.

What Others Are Not Telling You

The Professional package comes in at a minimum cost of $890 per month and requires an additional one-time cost of $3,000 to cover the onboarding cost. This would be the cheapest way to do any kind of email testing using HubSpot. However, for those who want to test for HubSpot itself, they could find that ActiveCampaign or Klaviyo offer a better deal for their needs.

Watch Out For

Two variants maximum is the most restrictive limit in this entire comparison. At $890/month, a two-variant cap is a meaningful limitation that several G2 reviewers call out directly as a disappointment given the platform's price point and overall capability.

Pricing

Best For

Mid-size to enterprise B2B companies already on HubSpot CRM that want email testing with native revenue attribution without adding a separate tool to the stack.

Review

"A/B testing in HubSpot gave us the tools we needed to refine our messaging, while simultaneously increasing our landing page conversion rate to an incredible 45%." — Adam Goyette, VP of Demand Generation at G2, HubSpot Case Study.

8. Omnisend

Omnisend is built specifically for ecommerce, and every part of its A/B testing reflects that focus. Testing is available on all plans, including the free tier; revenue attribution is built into automation split testing, and the Campaign Booster feature effectively runs an automated subject line re-test on every send without any manual setup.

How A/B Testing Works Here

Subject line and sender name testing is included in campaign testing for all plans, while content testing is available for paid plans only. Campaign Booster detects non-openers and sends again with a new subject line without any extra steps required from you. This acts as a light A/B test that gains some more opens for you automatically. In split flow within our automation builder, users can be split into two branches and measure the revenue from each path.

What Others Are Not Telling You

Campaign Booster is undervalued in virtually all Omnisend reviews. If you are using a basic newsletter campaign program, you can get an automatic recovery rate of 10-15% for lost openers without implementing an A/B test at all. In case you have a small team that cannot allocate time for running proper A/B test campaigns, then Campaign Booster is a solution for you.

Watch Out For

Omnisend specializes in ecommerce. Fewer template options, trigger actions, and integrations will be relevant to SaaS companies, professional service providers, or content companies compared to what you would get from ActiveCampaign or HubSpot. When not dealing with a retail model, the e-commerce-specific functions become neutral.

Pricing

Best For

Ecommerce brands on Shopify, WooCommerce, BigCommerce, or Wix that want A/B testing and automation split testing from day one without paying for a premium plan.

Review

"Omnisend helps us clearly see which actions drive ROI. We can distinguish not just between different popups but also between their versions, thanks to A/B testing. It shows exactly how much revenue each campaign and automated flow generates." — Irina T., CEO, Consumer Services, G2.

Conclusion

The choice will depend on which testing is important. The top automation testing in the medium market rate is ActiveCampaign. For ecommerce with attributed revenue, the best candidates are Klaviyo and Omnisend. If you want testing through AMP interactive emails, Mailmodo is the way to go. With a limited budget, MailerLite provides the best testing capacity without spending too much money. HubSpot is not worth its cost except when you’re within the HubSpot ecosystem.

In terms of plans, the majority offer free trials and free plans. Try them out on actual campaigns first.