How to Choose an Email Marketing Agency

Choose an email marketing agency on flow revenue, account ownership and spam rate, and run a six-step check before you sign, well ahead of Black Friday.

By Yannis Spanenburg · 2026-10-22 · 6 min read

In OpenSEO data, US searches for "email marketing agency" reached 18,100 in October 2025, against 1,300 the month after. Owners hire in a hurry before Black Friday.

What is an email marketing agency?

An email marketing agency plans, builds and runs the emails a business sends to its own list: automated flows such as welcome, abandoned cart and post-purchase, plus scheduled campaigns. A good one also owns deliverability, list growth and reporting, and ties every send to revenue or booked enquiries inside a platform like Klaviyo or Brevo.

• Hire an email marketing agency on its flow work first: Klaviyo's benchmark data shows flows earn about 41 percent of email revenue from 5.3 percent of sends.
• Keep the Klaviyo or Brevo account, the sending domain and the list in your company's name, and give the agency user access.
• Judge an agency on revenue per recipient, click rate and spam rate, because Apple Mail Privacy Protection makes open rates unreliable.
• Get the deliverability setup in writing: SPF, DKIM, DMARC and a spam rate under Google's 0.3 percent limit.

What does an email marketing agency do for a store or a service business?

For a Shopify store, the agency builds and maintains flows in Klaviyo, plans the campaign calendar, grows the list through signup forms and segments buyers by what they bought and when. For a service business on Brevo, the work centres on enquiry follow-up, appointment reminders and bringing past clients back.

How much of your email revenue should come from flows?

Flows should carry a large share of email revenue, because they fire on behaviour and reach people when they are closest to buying. Klaviyo's published email benchmarks, checked in October 2026, report that flows generate about 41 percent of email revenue from 5.3 percent of messages sent, with revenue per recipient around 18 times that of campaigns.

In our client work across Shopify stores and service businesses we keep seeing the same pattern: the welcome, abandoned cart and post-purchase flows were built at launch and left alone while the agency's hours went into campaigns. Our lifecycle email and SMS work for a US store shows what rebuilding that layer involves.

If the abandoned cart sequence is the weak point, read why an abandoned cart flow stops converting first.

Who should own the Klaviyo or Brevo account and the subscriber list?

Your company should own the account, the sending domain and the list, and the agency should log in as a user you can remove. The subscriber list is a business asset built from your traffic and your customers' consent. When the agency holds the login, the flows, segments and send history leave with it on the day the contract ends.

Which metrics should an email marketing agency report?

An email agency should report revenue per recipient by flow and campaign, click rate, unsubscribe rate, spam complaint rate and list growth. Open rate belongs at the bottom of the report. Since Apple introduced Mail Privacy Protection, Apple's servers pre-load the images in Apple Mail, so an open registers whether or not a person read the email.

Litmus reported in 2021 that about half of all email opens happen in Apple Mail, and its guide to Apple Mail Privacy Protection for marketers moves testing to clicks.

Google's bulk sender rules, in force since February 2024, require senders of 5,000 or more messages a day to Gmail to keep spam complaints below 0.3 percent and authenticate with SPF, DKIM and DMARC, as Close's guide to the Google and Yahoo requirements sets out.

The domain setup is covered in why emails go to spam in 2026.

Klaviyo also credits sales inside its own attribution window, the gap explained in why Meta shows more conversions than Shopify.

How to choose an email marketing agency in 6 steps

Run the selection the way you would audit your own program: start from your data, then make each agency show how it would change it. The six steps below take about two weeks and leave you with a written comparison you can defend to a partner, a board or your own finance lead.

1. Export the last 90 days of revenue by flow and by campaign from Klaviyo or Brevo before the first call.
2. Give each shortlisted agency read-only access and ask for a written audit of that account.
3. Ask each agency to name the three flows it would rebuild first and the reason for each one.
4. Request one case study with a starting point, what changed and the result, linked to a live client page.
5. Confirm in writing that your company owns the account, the sending domain, the templates and the list.
6. Agree on the reporting metrics and the spam rate ceiling before you sign the scope.

What are the warning signs in an email agency proposal?

The clearest warning signs are a guaranteed result, an offer to buy or rent a list, and a report built around open rates. Each one shows the agency selling activity it controls in place of results you can verify, and each one appears in the proposal itself, so you can catch it before you sign.

• A guaranteed revenue figure before the agency has seen your account data.
• Any offer to buy, rent or scrape contacts.
• An account opened under the agency's company name, or sending from the agency's shared domain.
• A monthly report led by open rate with no revenue per recipient or spam rate.

How does Proof of Pixel run email marketing?

Proof of Pixel runs email inside the same system as the website and the tracking: Klaviyo for stores, Brevo for service businesses, in accounts the client owns from day one. We start with read-only access, audit the flows and the data, give a range, then fix one price once we have seen the account.

Proof of Pixel is a marketing and consulting agency for businesses that live on enquiries and orders, building the website, the tracking and the follow-up as one system, with offices in Dubai, New York, London, Antwerp and Malaysia. Email sits inside our marketing service.

Proof of Pixel's position: an email agency should work inside an account the client owns and report revenue per recipient by flow before any open rate.

For an audit of your own account, send us your platform and list size.

Pull Your Flow Report Before the First Agency Call

Open Klaviyo or Brevo, export revenue by flow for the last 90 days and list every flow nobody has edited this year. That one page shows where the money sits and gives every agency the same brief.