What is email preheader text?

Safe subject line testing balances learning against engagement risk. You want to discover what works without sending underperforming variants to your entire list.

Standard approach: Split test sample—send variants to 10-20% of your list (split evenly between variants), wait for results (typically 1-4 hours depending on list size and open patterns), then send winner to remainder. Most ESPs automate this flow.

Best practices: Test one element at a time—don't change subject, preheader, and sender name simultaneously. Define winning metric—usually opens for subject tests. Ensure statistical significance—small samples produce random results. Document learnings—build a knowledge base of what works for your audience. Test continuously—audience preferences evolve.

Every send is a testing opportunity. Even without formal A/B tests, track subject line performance over time. Which approaches get higher opens? Which fall flat? Build institutional knowledge. Testing isn't a special event—it's how professional senders continuously improve.