Email marketing agencies: how to work with one (or build your own service)

What an email marketing agency actually does

An email marketing agency manages some or all of a client's email programme on their behalf. The scope varies significantly between agencies. Some offer end-to-end managed services covering strategy, platform setup, list management, copywriting, design, automation build, campaign execution, and reporting. Others specialise in a narrower slice: some focus exclusively on ecommerce email flows, others on B2B nurture sequences, others on deliverability and technical setup.

The distinction matters when you are evaluating agencies. A full-service agency that covers strategy through to execution suits brands that want to hand off the entire email function. A specialist agency that focuses on Klaviyo flow builds suits a brand that already has internal capacity for campaign management but needs someone to build the automation layer correctly. Understanding what you need before you start talking to agencies prevents the common mistake of hiring a generalist when a specialist would produce better results for your specific situation.

Most email marketing agencies operate on a retainer model, where a fixed monthly fee covers an agreed scope of work. Project-based engagements are also common for one-off pieces of work such as a platform migration, a flow audit and rebuild, or a deliverability investigation. Some agencies offer a hybrid: a lower retainer that covers strategy and oversight, with project fees for execution work above a set volume.

For context on how email fits into the wider ecommerce marketing stack, the ecommerce email marketing guide covers flows, campaigns, and platform selection in depth.

When to hire an email marketing agency vs DIY

The decision between managing email in-house and hiring an agency comes down to four factors: internal capacity, technical complexity, programme maturity, and the cost of underperformance.

Internal capacity is the most common driver. A marketing team of two people running a full ecommerce operation does not have the bandwidth to build and optimise a complete email programme alongside everything else they manage. An agency adds capacity without the cost and commitment of a full-time hire, and brings expertise that takes years to build internally.

Technical complexity matters for brands with large catalogues, complex segmentation requirements, or custom integrations between their store platform and email tool. Setting up a Klaviyo programme with 15 flows, dynamic product recommendation blocks, and predictive send time optimisation requires deep platform knowledge that most in-house marketers do not have unless email is their primary specialism.

Programme maturity affects the calculation differently. A new brand setting up email for the first time benefits most from agency support during the build phase, when the foundational decisions about platform, flow architecture, and list structure are made. An established brand with a mature programme may need agency support for specific optimisation projects rather than ongoing management.

The cost of underperformance is the factor that is most often underweighted. An email programme that contributes 15 percent of revenue instead of 25 percent because it was set up without specialist expertise is losing real money every month. The agency fee that closes that gap typically pays for itself quickly.

How to evaluate and choose an email agency

Evaluating email marketing agencies requires looking beyond case studies and pitch decks. The questions that reveal whether an agency is right for your business are specific to your situation, your platform, and your goals.

Platform expertise

Ask which platforms the agency works with and how many clients they currently manage on each. An agency that manages 30 Klaviyo accounts has substantially more Klaviyo expertise than one that uses it for three clients alongside ten other platforms. Platform depth matters because the best results in email come from using platform features that most users never touch: predictive analytics, dynamic content blocks, A/B testing at the flow level, and advanced segmentation logic.

Vertical experience

Email strategy for an ecommerce fashion brand is meaningfully different from email strategy for a B2B SaaS company. An agency that has worked primarily in your vertical will bring proven frameworks and benchmarks that a generalist agency will need to develop from scratch on your account. Ask for examples of work in your sector and the specific results achieved.

Reporting and transparency

Before signing any engagement, understand exactly what reporting you will receive, how often, and what metrics the agency will be accountable to. Agencies that are genuinely confident in their work welcome clear performance benchmarks. Agencies that resist specific accountability often lack the track record to commit to them.

Finding and vetting email marketing agencies can be done through specialist freelance platforms. Upwork lists email marketing specialists with verified work histories and client reviews. Fiverr covers shorter-term or project-based engagements with vetted email specialists. For agencies rather than individual freelancers, professional networks and referrals from businesses in your sector remain the most reliable sourcing channel.

For a comparison of the email platforms that most agencies build on, the best email marketing services guide covers Mailchimp, Klaviyo, HubSpot, and others across key criteria including deliverability, automation depth, and pricing.

Building email marketing as an agency service

For agencies that want to add email marketing to their service offering, the business case is strong. Email is a recurring-revenue service: clients need ongoing campaign management, list maintenance, and performance optimisation month after month, which makes it a natural fit for retainer-based agency work. The skills required overlap significantly with content marketing, copywriting, and digital strategy that many agencies already provide.

Building a credible email marketing service requires three things: platform expertise, a repeatable delivery framework, and the ability to demonstrate results. Platform expertise means knowing one or two email tools deeply rather than superficially knowing many. Most agencies that build strong email practices focus on either Klaviyo for ecommerce clients or HubSpot for B2B clients, with Mailchimp as a secondary option for smaller clients or those earlier in their email journey.

Building a repeatable delivery framework

A repeatable delivery framework is what separates agencies that scale email as a service from those that rebuild everything from scratch for each client. The framework covers onboarding (platform audit, list health check, integration setup), strategy (flow architecture, campaign calendar, segmentation model), execution (template builds, copy production, campaign scheduling), and reporting (monthly performance review, optimisation recommendations).

Project management tools like ClickUp and Notion work well for managing the delivery framework across multiple client accounts. A shared workspace where each client has their own project board, with standardised task templates for each phase of the engagement, keeps delivery consistent and makes it easier to onboard new team members without disrupting existing accounts.

Pricing email marketing as a service

Email marketing agency pricing typically falls into three tiers. Entry-level retainers covering campaign management for small lists with two to four sends per month sit between £500 and £1,500 per month. Mid-tier retainers covering full campaign management plus flow maintenance and monthly reporting sit between £1,500 and £4,000 per month. Full-service engagements covering strategy, all flows, all campaigns, copywriting, design, and weekly reporting sit above £4,000 per month for most markets.

Project fees for one-off work such as a complete flow build, a platform migration, or a list cleaning and re-engagement project are typically quoted separately. A full Klaviyo flow build covering welcome, abandoned cart, post-purchase, win-back, and browse abandonment for an ecommerce client typically ranges from £3,000 to £8,000 depending on complexity and the number of conditional branches required.

Tools for running client email campaigns

Running email marketing across multiple client accounts requires tools that support multi-account management, collaborative workflows, and clear separation of client data. Most major email platforms support agency or partner accounts that allow an agency to manage multiple client accounts from a single login with appropriate permissions for each client.

Mailchimp offers an agency partner programme with multi-account management. Klaviyo has a partner programme for agencies that includes co-marketing support, priority support access, and a partner directory listing. HubSpot runs a similar partner programme with tiered benefits based on the number and size of clients managed on the platform.

For campaign asset production, Canva supports team accounts where brand kits can be set up separately for each client, keeping design assets organised and accessible to the relevant team members without cross-contamination between accounts. Google Drive handles brief storage, copy drafts, and reporting documents in a shared workspace that clients can access with view or comment permissions.

For prospecting and growing the agency's own client base, Apollo supports outbound sequences to potential clients, with contact data filtered by industry, company size, and job title to reach marketing directors and heads of ecommerce who are the most likely buyers of email marketing services.

For a full picture of the campaigns and reporting structures that agencies need to deliver for clients, the email marketing campaigns guide covers brief-to-send planning, UTM tracking, and performance analysis in detail.

What this means for your agency or outsourcing decision

Whether you are evaluating an agency as a client or building email as a service on the agency side, the fundamental question is the same: does the email programme justify the investment it requires?

For brands considering outsourcing, the answer depends on the gap between your current email performance and what a well-built programme could deliver. An agency that closes a 10-percentage-point gap in email revenue contribution on a store doing £2 million annually is worth considerably more than its monthly retainer. The evaluation should be built around that potential return, not the cost of the retainer in isolation.

For agencies building email as a service, the answer depends on the depth of expertise you can genuinely offer. A service built on shallow platform knowledge and generic templates will produce mediocre results that do not retain clients. A service built on deep platform expertise, a structured delivery framework, and clear performance accountability will retain clients, generate referrals, and produce a margin that makes email one of the most profitable services in the agency's portfolio.

For a view of the reporting structures that demonstrate value to email marketing clients, the email marketing reporting guide covers the metrics, dashboards, and presentation formats that make performance visible to clients and stakeholders.

Agency tools and workflow management

Running a well-organised email marketing agency practice requires more than platform access. The operational layer, covering how briefs are taken, how copy is reviewed, how campaigns are approved, and how results are reported, determines whether the service scales or creates chaos as the client roster grows.

A brief-to-approval workflow that runs through Notion or ClickUp keeps campaigns on track across multiple accounts. A standardised brief template that captures the campaign goal, audience segment, send date, subject line options, and copy brief means copywriters and designers have everything they need without back-and-forth. Approval stages are built into the project board so clients can review and sign off without email chains that are difficult to track.

For copy production at scale, ChatGPT and Claude accelerate first-draft production for campaign emails, subject line variations, and A/B test copy. The agency's copywriter edits and brand-aligns the output, which is faster than writing from a blank page. This approach works best when the AI tools are given a detailed brief including the audience, the campaign goal, the tone of voice, and two or three examples of previous emails that performed well for that client.

Reporting across multiple client accounts is one of the most time-intensive parts of agency email management. Google Analytics provides the revenue attribution layer that sits alongside platform-native reporting. A standardised monthly report template in Notion or Google Slides that is updated with each client's data keeps reporting consistent and reduces the time required to produce client-ready documents each month.

For lead generation to grow the agency's own client base, Apollo handles outbound prospecting with targeted sequences to potential clients, while Upwork and Fiverr provide inbound enquiry channels for agencies that offer project-based services alongside their retainer work.