Mailchimp’s API does not return email-activity data at the parent campaign level for A/B or multivariate campaigns. This isn’t a problem with our integration, it’s intentional behaviour based on how Mailchimp structures these campaigns.
How does Mailchimp structure A/B test campaigns?
An A/B test in Mailchimp consists of a parent campaign and several child campaigns. Each version of the test, such as different subject lines or different content, is delivered as its own child campaign with its own campaign ID.
Because of this:
- The parent campaign is never actually sent to recipients.
- Only the child campaigns have delivery and engagement.
- Mailchimp does not aggregate open/click activity back into the parent.
How does MC4SF handle this?
In releases after version 1.185, MC4SF resolves this automatically using Mailchimp’s sub-reports. During the campaign sync we discover the Winner and Combo variants of each A/B or multivariate campaign, create them as child campaign records linked to the parent, and store per-recipient email activity (opens, clicks, bounces, etc) against those child campaigns.
On the Campaign Detail modal, a Variant picklist lets you switch between Winner and Combo variants on both the Members tab and Email Preview, so you can see exactly who received each variant and what it looked like.
This behaviour is controlled by the Sync Variate Children setting, which is on by default. Support may turn it off for an org if desired, to manage storage or callout limits.
Reporting upgrades are currently in progress. In the meantime: you can filter a Mailchimp Campaign report on the shared Campaign Settings Title to analyze the child campaigns. For example: Mailchimp Campaign Settings Title STARTS WITH 'New Member Email | '. Including the pipe limits your report to the variate campaigns only.
What about older versions?
On versions 1.185 and earlier, email activity for A/B and multivariate campaigns is not synced, because the parent campaign has no activity of its own and the child campaigns were not processed. If your installation existed before that release, (approximately September 2026), please contact us to enable the feature.
When you enable it, the next sync will re-align the data. Note that we will not delete the Sent emails that may be currently stored in the parent campaign, but those are duplicative and can be deleted manually or with a purge and refresh.
