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Process GuideApril 12, 20266 min read
How to Split-Test Cold Email Without Tanking Deliverability
Split test safely.
split testdeliverabilitytestingTest Rules
| Rule | Detail |
|---|---|
| One variable | Subject OR body. Never both. Isolate cause. |
| Minimum sample | 50-100 per variant. Less = noise. |
| Spread sends | Don't blast test in 1 hour. Same cadence as normal. |
| Same list quality | Split randomly. Don't test best vs worst list. |
When to switch copy: switch copy. Copy that 3x'd reply rate: copy change. Bounce rate: reduce bounce.
Volume Cap
Stay within your usual daily send limit. A test that doubles volume for a day can trigger spam filters. Split your normal volume between variants.
FAQ
Will testing hurt my domain?
Only if you send huge volume spikes or test spammy copy. Normal A/B at modest volume is fine. See how to warm up cold email domain.
What to test first?
Subject line. Biggest lever. Then first line of body. Then full body.
How long to run a test?
Until you have 100+ sends per variant, or 1-2 weeks. Don't stop early.