How can I A/B test email body copy?

Testing email body copy requires isolating specific elements while measuring engagement beyond opens:

Isolate your variable: Test one change at a time. Different opening paragraphs OR different offer framing OR different story approaches, not all three.

Keep everything else constant: Same subject line, same images, same CTA, same send time. Only the body copy element should differ.

Measure downstream metrics: Body copy does not affect opens (recipients have already opened). Track clicks, conversions, revenue, and engagement depth.

Test meaningful differences: "Free shipping included" versus "Your order ships free" is too subtle. "30% off everything" versus "Buy one, get one free" tests different offer structures meaningfully.

Body copy tests take longer to show results because they depend on recipients reading, not just opening. Plan for larger samples and longer durations.