As a marketer, it's essential to continually experiment and optimize your campaigns for better performance. One of the easiest and most effective ways to do this is through A/B testing. SendX allows you to run A/B tests on subject lines to determine which variation performs best—based on open rates—before sending the winning version to the rest of your audience.
Before You Begin
Make sure you:
Have an active SendX account
Have your email content ready
Know the subject line variations you’d like to test
Have a clear understanding of your contact list
Step-by-Step Instructions
1. Navigate to A/B Split Testing
Log in to your SendX dashboard
Go to Campaigns > A/B Split Test from the main menu
2. Create a New A/B Test
Click Create A/B Split Test
Enter a campaign name and select the "From" email address
Add Subject Line Variations
Under Variations, enter at least two subject lines you want to test
Click on Add Subject Line Variation to add more versions if needed
Design Your Email
Choose an email template under the Design step
Proceed to the Content section to edit your message
Choose Recipients and Set A/B Split
Select the recipients for your campaign
Under “Percentage of contacts sent each A/B Subject Line Variation”, choose what portion of your list will receive the test emails
Example: Selecting 40% means 20% will receive version A and 20% will receive version B. The remaining 60% will receive the winning subject line.
Set Timing for Winner Evaluation
Under "Send winner A/B Subject Line Variation based on open rates to remaining contacts", select the duration (in hours or days) SendX should wait before choosing the winner
SendX will analyze open rates and automatically send the best-performing subject line to the remaining contacts
Schedule or Send the Campaign
In the final step, choose to send immediately or schedule your campaign
That’s it! SendX will take care of the rest
Tips & Best Practices
🧪 Test regularly to optimize your messaging and engagement
💬 Make sure your subject lines are clear, concise, and compelling
📊 Give your test enough time (2–24 hours) to gather meaningful data
🎯 Use A/B testing not just for subject lines, but also "From" names, content blocks, and CTAs
Conclusion
With SendX’s A/B testing feature, you can effortlessly test subject lines on a random sample of your audience and let the platform choose the best-performing one based on real engagement. This ensures you’re always sending the most optimized version of your email, improving open rates and driving better results.
Have more questions or need help setting up your first A/B test? Reach out to our support team—we’re happy to assist!