A/B Test Email Subject Lines Automatically
Every morning, WebRun opens Mailchimp, checks any active A/B subject-line tests for a winning result, reads the open rates for each variant, logs the data in a Google Sheet, and sends a Slack digest declaring the winner and recommending the send decision.
How can I automatically monitor and report the winner of an email A/B subject-line test?
WebRun checks your active Mailchimp A/B subject-line tests every morning, reads the open rates for each variant, logs the data in Google Sheets, and posts a Slack digest declaring the winner and the recommended send decision - so your full list gets the higher-performing subject line.
- Win every subject-line test without manually checking results
- Send to your full list with data-backed confidence
- Results logged in Sheets for ongoing benchmarking
Built for email marketers · e-commerce teams · SaaS marketing teams · agencies
What does WebRun do on every run?
The exact actions WebRun takes, in order - in plain language, so you can adjust anything.
-
WebRun signs in and gets to work
Opens
mailchimp.comin a real browser with your saved login - no setup, no API keys. -
1
Mailchimp - read A/B test results for active campaigns
mailchimp.com
WebRun opens Mailchimp to read A/B test results for active campaigns. - Open Mailchimp and navigate to Campaigns then filter to A/B tests
- For each test that has reached statistical significance or its time limit, open the Results tab
- Capture Subject Line A and B, open rate for each, click rate, and whether a winner has been auto-selected or is pending your decision
Done when Results for all active A/B tests are captured with variant performance data.
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2
Google Sheets - log variant performance data
google.com
WebRun opens Google Sheets to log variant performance data. - Open the Email Test Results sheet
- Append a row per test: campaign name, both subject lines, open rate A vs B, click rate A vs B, and the declared winner
- Update the running win-rate for each subject-line style to build pattern intelligence
Done when Test results are logged with both variant metrics and the pattern tracker updated.
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3
Slack - report the winner and recommend next step
slack.com
WebRun opens Slack to report the winner and recommend next step. - Post a Slack digest to #email-marketing: winning subject line, open rate comparison, and a send recommendation
- If neither variant has reached significance yet, report the current lead and recommend waiting
Done when You have a Slack message with the winning subject line and a clear send recommendation.
How is each run configured?
Secure by default
Connect once, stays signed in
WebRun signs in once and keeps each session in a persistent environment, so every run picks up right where it left off.
Every action is checked against this policy before it runs.
Questions, answered
Will it send the winning variant to the full list automatically?
No. It reports the winner and recommends the action - you make the final call to send in Mailchimp. Nothing is sent without your click.
How does it pick the winner?
It reads whichever metric you configure as the primary goal - open rate by default, or click rate if you prefer. You can also ask it to wait for statistical significance before calling a winner.
Can it help me write better subject lines over time?
Yes. It tracks which styles win across tests in the Google Sheet, and you can ask WebRun to summarise the patterns to inform your next campaign.
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