A/B testing sends two or more variants of a message to random samples and measures which performs better on a chosen metric before sending the winner to the rest.
What should I A/B test first in email?
Subject lines, then the primary call to action, then send time. These have the largest measurable effect.
Why does email A/B testing matter for deliverability?
Opinions about subject lines and layouts are unreliable; tests turn them into evidence and compound small gains over time.
What is the first step to get started with email A/B testing?
Choose one variable per test and one primary metric (clicks or revenue, not opens).
What is the most common email A/B testing mistake?
Testing several changes at once.