Subject lines are the single biggest lever for improving email engagement. Instead of relying on guesswork or manual A/B testing, Optimove’s Content Decisioning automates the process.
Optimove’s Subject Line Testing makes it effortless: instead of guessing or running manual A/B tests, the system automatically tests up to four subject line variants in any recurring OptiMail campaign, learns from performance, and rebalances distribution day by day. The result: measurable uplift in opens and clicks, without extra effort.
This guide will walk you through how to set up and send a Subject Line Test, from creation to campaign execution.
Step-by-Step: How to Set Up a Subject Line Test
Step 1: Choose your Template
Select a pre-existing template or create a new one.
Instructions:
- Navigate to Plan → Templates → OptiMail
- Select an existing template or create a new one.
- Draft your campaign subject line.
- Click “Add Subject Line Test”.
Step 2: Generate Subject Line Variants
Instructions:
- In the "Subject Lines" window, select how many variants you’d like to test (up to four).
- Enter subject lines manually or use GenAI Assistance to generate options based on your prompt.
- Edit or regenerate variants as needed.
- Click Save to activate the test.
Generated subject line variants can be edited, deleted, or regenerated:
An active subject line test in the OptiMail template editor:
Step 3: Set up and Send Recurring Campaign
Instructions:
- Go to Execute → Campaign Builder, or use the Run Campaign button in the header.
- Choose Scheduled Recurring Campaign (this is required for Subject Line Testing).
- Select the template where you enabled the Subject Line Test.
- Preview your campaign and send.
Step 4: View Campaign Results
Instructions:
- Navigate to Mission Control.
- Open the campaign’s Channel Metrics window by clicking on the performance stats.
- Click Template & Content Variations Breakdown for detailed results.
- Review uplift, open/click rates per variant, and see the leading variant (indicated by a trophy icon).
The Template & Content Variations Breakdown shows the performance of each subject line.
How Content Decisioning Works
For now, Content Decisioning is available only for scheduled recurring campaigns.
- Day 1: All chosen variants are split evenly across the audience to establish a baseline.
- Day 2+: Send weights are adjusted automatically based on open and click performance data from the previous day(s).
- Dynamic testing: This is not a “winner-takes-all” system. All variants continue to be tested throughout the campaign, but top performers receive a greater weighting to maximize engagement.
Because Content Decisioning focuses on variations within a single template, it can be paired with other test types, such as AI Offer Decisioning Agent (formerly Self-Optimizing Campaigns), to create even more dynamic campaigns.
How is Campaign Uplift Calculated? The Optimization Benefit Percent measures the success of the content decisioning by comparing your actual results to a simulated baseline.
- Actual Results: The opens and clicks your campaign received after the system automatically sent more traffic to the best-performing subject lines.
- Baseline Simulation: An estimate of the results you would have gotten if traffic had been split evenly between all variants for the entire campaign.
This percentage represents the performance lift gained by using automated optimization instead of a simple A/B test.
Use Case Examples
- E-commerce Promotions: Test urgency-driven subject lines (“Today Only: 40% Off”) vs. value-driven ones (“Save 40% on Your Next Order”) to see which drives more opens.
- Content Publishers: Compare straightforward headlines (“Top Stories for You”) with curiosity-driven ones (“You Won’t Believe Today’s Headlines”).
- Seasonal Campaigns: Try festive subject lines (“Holiday Deals Inside”) against personalized ones (“[First Name], Your Holiday Offer”).
- VIP Segments: Test exclusivity messaging (“For VIPs Only”) vs. reward framing (“Your Exclusive Gift Awaits”).
Full Example Recap
| Step | Action | Details |
|---|---|---|
| 1 | Choose Template | Select an existing or create a new OptiMail template, then click "Add Subject Line Test". |
| 2 | Generate Subject Line Variants | Use GenAI Assistance to create up to 4 subject line variants that adhere to Brand Guidelines. |
| 3 | Set up Campaign | Create a recurring campaign with the selected template. |
| 4 | View Results | Monitor campaign performance in Mission Control to see which subject line variants perform best. |
FAQ
Is Content Decisioning the same as the AI Offer Decisioning Agent?
No. Content Decisioning focuses on content-level optimization (e.g., subject lines within a single campaign). The AI Offer Decisioning Agent operate at the orchestration level, choosing which campaigns to send to a customer. You can use both together for maximum impact.
Can I combine Subject Line Testing with other campaign tests?
Yes, Content Decisioning is supported with the AI Offer Decisioning Agent. However, we recommend using Content Decisioning in a standard recurring campaign, not with the AI Offer Decisioning Agent, since they optimize at different levels. Keeping one optimization layer at a time ensures cleaner results and clearer attribution
How many subject lines can I test at once?
You can test up to four variants per recurring campaign.
Do I need to pick a leading variant manually?
No. The system continuously rebalances delivery based on performance. However, you can see the leading variant in Mission Control (marked with a crown icon).
Does this work for one-time or ad hoc campaigns?
Not yet. Subject Line Testing is currently limited to scheduled recurring campaigns.
How soon will I see results?
Day 1 establishes the baseline performance for all variants. Starting on Day 2, the system will begin shifting distribution weights based on real engagement data.