How to Choose the Best Email Marketing Agency for Your Ecommerce Brand

By Emiel Dingemans, Founder of Magicianly

Updated November 2026

We're an email and SMS retention agency, so we have a stake in this topic. We wrote this so you can hold any agency to the same tests, including us.

The best email marketing agency for an ecommerce brand is the one that can prove it changes what customers do after the first order, and that is honest about what email did and didn't cause. Judge every agency on seven tests: what it measures, how it handles attribution, who does the work, whether it brings ideas, what proof you can verify, how deep its Klaviyo and lifecycle skills go, and whether it tells you when email isn't the problem.

Every agency says it will grow your email revenue. That tells you almost nothing, because nearly any agency can send emails that get credit for revenue. What separates a good one is what happens to your customers. Do more first-time buyers come back? Does a bigger part of your revenue come from people who already bought?

Here's how we'd test an agency before signing anything. The same tests apply to us.

What Does the Best Email Marketing Agency for Ecommerce Actually Do?

It owns the customer lifecycle in email and SMS, not just the next send. That means signup forms, welcome and abandonment flows, post-purchase, winback, campaigns, segmentation, deliverability and testing, all pointed at one goal: getting customers to buy again.

Agencies aren't interchangeable, though. Some are built for production volume, some for very large global brands, some for email plus paid ads. The best one for you is the one whose strength matches what's actually holding your store back.

If you want named agencies side by side, see our comparison of the best ecommerce email marketing agencies and the best Klaviyo agencies. This page is about how to judge whoever ends up on your shortlist.

What Are the 7 Tests of a Good Email Marketing Agency?

Use this as a scorecard on your calls. Each test is explained below the table.

Do They Measure What Customers Do Next, Not Just Email Numbers?

Open rates and clicks tell you how email is running. They don't tell you whether your business is healthier.

Ask what the agency will track beyond them: how many first-time buyers place a second order, how long that takes, what share of store revenue comes from repeat customers, and LTV by cohort. A good agency can tell you which flows and campaigns it would touch first to move those numbers. If you want the definitions, start with our guides on repeat purchase rate and customer lifetime value.

At GarageWorn, a seven-figure brand, repeat customers went from 8.6% to 14.9% of store revenue over five months. That's the kind of number we care about more than any open rate. You can read the full numbers in the GarageWorn case study.

Are They Honest About Attribution?

Attributed revenue is the revenue your email platform credits to email. It's a useful number, but it isn't the same as revenue email caused, because some of those orders might have happened anyway.

So ask how the agency separates email's impact from everything else going on in the store. A good answer looks at total store revenue, repeat customer revenue and cohorts next to the attributed number. For more on how this works in Klaviyo, see our guide to Klaviyo attribution.

Here's how we handle it. At SabersPro, a multi-million dollar brand, attributed email and SMS revenue grew about 50% over six months. Total store revenue grew 28.5% in the same period. The case study says so, and it says we're not claiming email did all of it. At GarageWorn, attributed revenue grew 124% while the whole store grew 66.3%, and the case study says that too. If an agency only shows you the biggest number, ask what the smaller one is.

Who Actually Does the Work?

In some agencies, the person who sells you isn't the person working in your account. Ask who will write, design and build, and whether you'll talk to them directly.

With us, you work with Emiel directly, not an account manager in between. Before founding Magicianly in 2019, Emiel spent five years working for large Dutch retailers like OFM and Dierspecialist, and he has been in ecommerce for more than 12 years. He also runs one of the largest YouTube channels in the world on email marketing for ecommerce, so a lot of how we work is public.

One client put it this way in a Trustpilot review:

"Emiel personally speaks with me regularly, and I have nothing but good things to say." - Luke Doughty

Do They Bring Ideas or Wait for Instructions?

You shouldn't have to chase your agency. A good one tells you what it's testing, what changed and what's coming next without being asked. It also comes to calls with ideas for your products, your customers and your calendar.

A simple test is to ask what they'd change in your account first. If you've run an email marketing audit, bring it. A specific answer beats a general one every time.

Another Trustpilot review says:

"They take time to get to know your business and product and as a result are able to create very high quality campaigns and flows." - Sergey Kogan

Can You Verify Their Proof?

Proof you can check beats proof you have to trust. Look for case studies that name the brand size and the time period, show the before and after, and include the caveats. Then look for reviews on a site the agency doesn't control.

We have a 4.7 out of 5 rating on Trustpilot from more than 30 verified reviews, and you can read them on our reviews page. The two case studies we use as examples here, SabersPro and GarageWorn, both show the before period, the after period and what else grew.

Our clients have generated $300M+ through retention channels. A number that size tells you little on its own, so ask any agency for the brand size, the time period and the caveats behind its headline figure, and hold us to the same standard.

Be careful with any agency that quotes huge percentages with no brand size, no time frame and no caveat. A big percentage from a tiny starting point isn't the same as steady growth on an established program.

How Deep Are Their Klaviyo and Lifecycle Skills?

Most competent agencies can build a welcome flow and send a campaign. The difference shows up in the harder parts: segmenting first-time and repeat buyers, building post-purchase and winback flows, protecting deliverability, and running tests properly.

Ask how they decide which flow to build next, and how they test. Our Klaviyo management service page shows what that work covers.

We're an official Klaviyo partner. Partner status can be a useful sign of platform experience, but it doesn't prove an agency will grow your revenue, so weigh it against the other tests.

Will They Tell You When Email Isn't the Problem?

Sometimes the bottleneck is traffic, the offer, the product page or the checkout. An honest agency says so, even when it means less work for them.

It should also be clear about who it isn't for. We're probably not the right fit if you only need a few templates designed, you want a low-cost one-off freelancer, you mainly need paid ads, or you want a large enterprise agency structure. We're built for established ecommerce brands that care about repeat purchase and LTV, where email and SMS are central to the retention stack.

What Do These Tests Look Like in Practice?

Here are the two examples we've used, side by side. We're showing the caveats on purpose, because that's test 2.

Where Do Lists of the Best Agencies Fit In?

A list is a good way to build a shortlist. It's a bad way to make the final decision. Use a comparison to find three or four agencies, then run the seven tests on each one.

Our two comparisons, the best ecommerce email marketing agencies and the best Klaviyo agencies, are a starting point. We're one of the agencies in them, so double-check us too.

How Much Should an Email Marketing Agency Cost?

It depends on scope: campaign volume, flows, SMS, design, strategy and reporting all change the price. We break down the pricing models and what drives them in our email marketing agency pricing guide.

One rule of thumb for this page: cheap isn't a test, and neither is expensive. Run the seven tests first, then compare quotes from the agencies that pass.

What Should You Check Before You Sign?

Run through this before you commit to any agency:

• You know who will work in your account and you've talked to them.
• They can explain which customer metrics they'll try to move first.
• They've told you how they handle attribution, and they didn't take credit for everything.
• You've seen at least one named case study with a time period and a caveat.
• You've read independent reviews.
• They've told you what they'd change in your account first.
• They can describe the first 90 days in writing.
• They've told you when they wouldn't be the right fit.

Are We the Right Fit?

Maybe. We're a good fit if you're an established ecommerce brand, you want strategy and execution in one team, and repeat purchase and LTV matter to you. We're not a good fit if you need a few templates, a cheap one-off freelancer or a paid ads agency.

If that sounds like you, we'll look at your account together and tell you honestly what we'd change first.