When conducting message tests, some email content variables consistently have a bigger impact on engagement. If you’re looking to optimize your email performance, start by testing these key elements for an outsized impact.
1. Email Topic and Value Proposition: The Biggest Driver of Engagement
By far, the most influential content variable is the topic and value proposition of the email. If your message doesn’t offer something relevant and valuable, no subject line hack or design trick will save it. The best-performing emails align the needs of your audience with the goals of your business.
Winning value propositions typically fall into one of these categories:
Increase Revenue: Helping your contacts make more money is always compelling.
Save Money: Cost savings and efficiency are major business drivers.
Innovation & Competitive Advantage: Staying ahead of the curve is a strong motivator.
Productivity: People are always looking for ways to work smarter, not harder.
Career Growth & Expertise: Professional development is a powerful incentive.
Before testing anything else, make sure your email’s core message is something your audience actually wants to hear. If you want more value proposition options, check out the Elements of Value for B2B and B2C companies developed by Bain and Company and published in the Harvard Business Review
2. Sender Name: Who It Comes From Matters
People don’t just open emails because of what they’re about—they open them because of who they’re from. Your sender name influences whether contacts trust and engage with your message.
Here are key sender name variations worth testing:
Person vs. Brand vs. Team: A brand name can be authoritative, but a personal sender often feels more relatable.
Individual Name Testing: Some audiences respond differently to male vs. female names or names from different cultural backgrounds.
A well-known or trusted sender can boost engagement, even if the email topic isn’t immediately compelling.
3. Tone of Voice: Authenticity Wins
Tone of voice is a subtle but powerful engagement driver. If the email is coming from a person, the tone should match their personality and style—otherwise, it feels inauthentic. If contacts sense that changing the sender name was just a tactic, engagement will drop.
Effective tones for email messaging include:
Clever & Witty: Humor and intelligence can make emails more memorable.
Casual Commiserating: A relatable, “we’re in this together” tone builds rapport and shows empathy.
Dry Humor: A subtle, sharp style can stand out in crowded inboxes.
Straightforward & Concise: No fluff, just the facts—this works well for time-sensitive or high-stakes content.=
The right tone makes the email feel personal, genuine, and worth reading.
4. CTA Placement & Wording: Making Clicks Easy
Your call to action (CTA) is one of the biggest factors in click-through rates. Contacts immediately look at the CTA for the most concise and direct summary of your offer. It should be clear, concise, and valuable from the contact’s perspective.
What to test:
CTA Placement: Does it work best at the top, middle, or bottom of the email?
CTA Wording: “Get Started” vs. “Claim Your Offer” vs. “Read More” – the phrasing can significantly affect response rates.
CTA Design – Button vs. hyperlinked text: some audiences prefer different formats.
The best CTAs make it obvious what the next step is and why it matters to the recipient.
5. Subject Line Detail & Specificity: More Detail, More Opens
Aside from topic, the other biggest driver of open rates is specificity. Vague, generic subject lines often get ignored, while detailed, precise ones tend to drive engagement.
Why? Because contacts don’t want to be strung along. They are constantly qualifying whether an email is worth their time. If you’re not upfront, they assume you’re hiding the real value behind a sales funnel.
Examples:
Vague: “Big News Inside”
Specific: “New Feature Saves Design Teams 3 Hours/Week”
The more concrete and transparent you are, the more likely contacts will open your email—and engage with what’s inside.
The Bottom Line: Test What Matters
If you’re serious about improving your email marketing, start by testing these high-impact variables. Your audience will tell you—through their opens, clicks, and responses—what works and what doesn’t. Focus on what delivers real value, and engagement will follow.
Learn more from our Message Testing tips and tricks and how to speed up your version development process with Generative AI.
