# Create A/B test campaigns

> Send two versions to a sample, let MailMachine pick the better one by clicks, and send the winner to the rest.

Source: https://www.kualo.com/knowledgebase/mailmachine-campaigns/create-a-b-test-campaigns
Updated: 2026-06-10

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:::info
A/B testing is an advanced feature available on selected plans. If you don't see **A/B Tests** in your account, it may not be included on your current plan - [get in touch](/knowledgebase/getting-started/how-to-create-a-support-ticket-in-mykualo) and we'll let you know your options.
:::

An A/B test (or split test) sends two versions of a campaign to a sample of your list, sees which gets more clicks, and then sends the winner to everyone else - so MailMachine picks the better email for you. It's one of the most reliable ways to improve your results over time. This guide covers setting one up.

:::warning
A/B testing needs a big enough sample to find a clear winner, since the decision is based on clicks. On a very small list, or a time-sensitive send, it may not reach a meaningful result in time - work out how long it'll take to gather enough clicks before you rely on it.
:::

## Set up an A/B test

1. Click the **Campaigns** tab and select **A/B Tests**.
2. Click the **+** to start a new test.
3. Name it, choose a list and segment, and click **Continue**.
4. Select the **test block** to open its distribution settings on the left:
   - By default, A and B are split 50/50.
   - Set the **test distribution size** and the **winner size**. For example, with a 40% test size and a 60% winner size, 40% of contacts receive the A/B sample and the better-performing version then goes to the remaining 60%.
5. Set the **winner criteria**: when the test ends, and a fallback email to send if no clear winner emerges (when there isn't enough of a difference to be statistically meaningful).
6. Select the **Email A** block, click **Edit**, and build it.
7. To reuse A's content as a starting point for B, click **Copy Email A Content to B**, then vary it.
8. Click **Save and Exit**, and do the same for **Email B**.
9. When you're happy, click **Start Test** at the top right.

Your test runs, and you'll find it in your A/B test drafts to analyse. You can rename, delete or duplicate it from the arrow menu.

## Troubleshooting

**A/B testing isn't available** - check it's included on your plan, and that your list is big enough to be meaningful.

**Results are inconclusive** - increase the sample size (around 1,000+ contacts is a sensible minimum), extend the test duration, and make sure your two versions are different enough to tell apart.

**Winner-selection issues** - review your criteria, always set a fallback email, and allow several hours for engagement to accumulate.

**Distribution problems** - make sure your test and winner percentages add up sensibly, and that your segments don't overlap.

For pre-send checks, see **[Testing your campaign](/knowledgebase/mailmachine-campaigns/testing-your-campaign)**. Stuck? [Open a support ticket](/knowledgebase/getting-started/how-to-create-a-support-ticket-in-mykualo).

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_Source: Kualo Knowledgebase — https://www.kualo.com/knowledgebase/mailmachine-campaigns/create-a-b-test-campaigns · © Kualo Ltd._