6 immediate benefits of using social proof in email subject lines
Written by
Puneet Mahajan
Puneet Mahajan

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6 immediate benefits of using social proof in email subject lines

Published : June 30, 2023

A survey of US-based consumers in January 2023 revealed that 87% of the respondents used Google reviews to evaluate local businesses in 2022. Not surprising since prospective customers naturally place more faith in existing customers than in what a brand says about itself. A brand has every reason to highlight its excellence and downplay its inadequacies. Customers who have spent money buying a product can be counted on to share their true experiences.

This is why brands hold (and must hold) social proof in high regard. When you can showcase that your customers are happy with what you’ve offered, you have a much better chance of convincing others to purchase. Displaying social proof is one of the easiest ways to gain people’s trust and persuade them to consider your product or service.

This article discusses how you can use social proof to positively add to your email campaigns, mainly when they appear in the email subject lines. When your leads see— up front and center—that customers like them approve of your brand, they will be much more inclined to give your product a shot.

Builds immediate trust

When someone sees that your products are liked and appreciated by unbiased, third-party users, they will immediately be assured that your brand is worth a look and, hopefully, a purchase.

Brands that lead with social proof in email subject lines are more likely to be considered authentic. By going with what customers say about them instead of their own marketing narratives, such brands create an impression of having nothing to hide. They’re not trying to convince you to buy something.

Instead, they’re letting the voices of their consumers talk and lead you into opening and acting on your email. This is as transparent as it gets and will surely get you brownie points in a world of double meanings and “fine print.”

If your product has earned multiple five or four-star ratings, folks will automatically take it seriously and feel more confident about placing an order. Showcase the star ratings or numerical scores in your subject line. It’s like getting a recommendation from a community – they have no reason to give you anything but an honest opinion you can trust.

Drives traffic to your site

A HubSpot report states that for 50% of all consumers, their next step after reading a positive review about a company is to visit their website. The more social proof you can demonstrate in the subject line, the more customers will open your email and flock to your site. All that’s left to do is to nudge them further in the purchase pipeline.


Conveys authority and confidence

People naturally trust leaders. If you can display some well-known names (across single or multiple industries) that have used your product or services and are pleased with them, your battle is half-won. This is especially relevant to B2B brands, so most B2B websites make their client logos highly visible. It is one of the easiest and most reliable ways to declare your expertise in the domain; it’s like saying, “The leaders trust us.”

While you cannot place a series of logos in subject lines, try including a brief and impactful client testimonial extract in the subject line. Let other people create trust in you.

Creates a sense of safety

Customers must enter their financial information to make a purchase, which they certainly won’t be willing to do if they don’t trust your brand. A solid number of positive reviews/testimonials/social proof helps put them at ease and more comfortable doing the transaction, especially for high-ticket items.

When people see social proof in the subject line, they are assured about your legitimacy even before they open the email. Naturally, they will be more receptive to your brand messaging and pay more attention to the email body.

Demonstrates a customer-first attitude

Any brand that showcases social proof knows well that no advertising is better than positive word-of-mouth. Companies with this awareness will always go the extra mile to make their customers happy because that’s how you get the 5-star reviews and “would buy again” testimonials.


Naturally, if your email subject lines lead with social proof, recipients are likely to think that you’re a brand that takes its customers seriously and puts in the work to create user experiences that leave folks wanting more of it (in a good way).

Saves the customer’s time and effort

We’ve already mentioned that internet-savvy folk (which is most of your customer base) will take their time to do research before supporting or even exploring a brand. Why not help them with the info they are looking for? Consider a subject line like, “50000 units sold in the last 72 hours!”

When you present social proof of mass buying in your email subject lines, you do half the work for the customer. You’re giving them peer assurance and making their lives easier. Putting in the effort to save your customers’ research time is sure to get you a lot of brownie points with them.


Not only will you impress prospects by doing the work for them, but you’ll also get them on your side with positive social proof. Dare we say that it’s a win-win?

But how exactly do you use social proof in your email subject lines?

We could write a whole article exploring this question and probably will. But for now, suffice it to say, there are multiple channels via which you can collect social proof and an equal number of ways to factor them into your email subject lines.

If you would like to implement the most advanced, AI-powered subject line optimization with social proof, get in touch with us.

Netcore has been recognized as “Ahead of the curve at applying AI to marketer workflow” in The Forrester Wave™: Email Marketing Service Providers Report 2022. For the second year in a row, we received the “Highest overall customer rating” as a Customers’ Choice in the 2022 Gartner Peer Insights “Voice of the Customer” Report.

Most importantly, we send over 20 billion emails a month on behalf of 6500+ businesses across 40 countries – so we’re constantly gathering data, carrying out optimization at different levels, and pushing for the highest achievable goals in email ecosystems.

Connect with us, and let’s talk about making email the highest ROI channel in your marketing strategy.

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Written By: Puneet Mahajan
Puneet Mahajan
Senior Product Specialist