How to Hire an Email Marketing Agency: The Complete Guide

Whether you’re a founder trying to unlock email as a revenue channel, a marketing lead evaluating agencies after an underperforming year, or a CMO looking to replace a partner that never delivered — this guide gives you a clear, honest framework to make the right hire.

The wrong agency costs you more than their monthly retainer. It costs you six months of stalled performance, a list you’ve burned through, and the opportunity cost of what a strong program would have built in that time.

If email is sitting at under 20% of your revenue, that’s not a channel problem. It’s a strategy problem.

Done right, email generates 20–40% of revenue for brands that have it properly managed. It returns $36–$42 on every dollar spent. The businesses hitting those numbers have one thing in common: someone owns the strategy, and they’re obsessive about it.

The email marketing agency market is full of providers who are better at pitching email than running it. This guide will help you find the ones who actually deliver — and avoid the ones who’ll cost you months to figure out.

What Does an Email Marketing Agency Do?

An email marketing agency is responsible for how your email channel performs over time. That means it brings together strategy, campaigns, automation, and optimization into something that works as a complete system.

Most brands focus on individual campaigns. What actually drives results is how segmentation, email marketing automation, subject lines, copy, and deliverability work together. A good agency understands those relationships and builds around them. That’s what moves conversion rates, retention, and consistency across the customer journey.

Types of Email Marketing Agencies

Email marketing agencies vary in how they operate. They are – 

• Full-service agencies take ownership of the channel. They handle strategy, execution, and performance, and work closely with your marketing team.
• Specialist agencies focus on specific areas such as automation, email copy, or deliverability. They are typically brought in to solve targeted problems.
• Freelance email marketers focus on execution. They are useful for smaller tasks but may not offer the depth needed for long-term performance.

What Sets A Good Email Marketing Agency Apart

Strong agencies approach email marketing as a system. They do not try to fix performance by sending more campaigns. Instead, they look at how everything is set up and fix what is not working. Then they improve how each part connects.

Studying analytics is also a big part of their work. It helps guide decisions and manage inactive subscribers to keep list quality strong. Over time, they improve email performance and make sure their work is aligned with your business goals. 

While most email marketing agencies will execute, only some improve. 

Read our complete blog on What does an email marketing agency actually do

Should You Hire an Agency or Build In-House?

This decision depends on what you need right now. Control or speed? Depth or flexibility?

Building in-house gives you full ownership. Your team understands your product, your customers, and your brand voice. But it takes time to hire and even more time to get everything working together.

Working with a hired email marketing agency gives you access to a full team from day one. You get strategy, execution, analytics, all of it, without building it internally. It works well when you need faster results and a more structured approach.

Here is how both options compare:

Some businesses choose a middle ground – a setup where a small internal team works with an agency on strategy or execution.

If you need control and have the resources, build in-house. 

If you need speed, structure, and consistent performance, an agency is usually the better choice.

For more insights, read our article on Agency Vs In-House: Which is better for you?

How to Choose The Right Agency?

Most agencies sound similar on the surface. All of them have the same services, same claims, same tools. What you need to focus on while choosing an agency is how they approach email marketing for your brand. 

Start by being clear on what needs to improve. For many brands, email contributes 20–40% of revenue, so the focus is usually on performance.

Here are some pointers to look out for when choosing an email marketing agency – 

Check if they understand your space. Ask what they typically see in businesses like yours. A strong agency will point out patterns in your customer journey and where performance usually drops.

Ask for specific results. Do not settle for general claims. Look for clear improvements in conversion rates, click-through rates, and proof of their other claims. Always ask what changed to drive those results. Good agencies connect outcomes directly to outcomes. 

Pay attention to how they prioritise. Ask what they would fix in the first 30–60 days. If the answer feels scattered or everything sounds urgent, there is no clear structure behind it. 

Clarify who is handling your account. Clarify who is handling your account — and how many others they manage. Most agencies assign one account manager to 10–15 clients. At that load, strategy becomes generic and execution loses depth. Top-tier agencies keep it at 2–3 clients per AM. That difference is where customisation either happens or disappears. Ask the number directly.

Watch how they communicate from the start. Notice how clearly they answer questions, how quickly they respond, and whether they actually address your concerns. This usually reflects how the working relationship will be.

Read more on How to choose the right email marketing agency

Red Flags to Watch Out For

If you analyze the email marketing agencies’ claims from the get-go, you’ll start noticing issues early on. And if you do notice them, it’s best to step back. 

Guaranteed results early. Email performance depends on multiple factors, so fixed outcomes usually mean the strategy will adjust later to match expectations.

Vague or unclear case studies. If results are not broken down or tied to specific actions, it is difficult to trust how performance was actually achieved.

Strategy that feels like a campaign calendar. When everything is about sending emails and not how they connect, long-term performance will stall.

Repetitive execution. If every campaign looks the same, there is no real testing or adaptation behind it.

Overloaded account management. When one person handles too many brands, strategy becomes generic, and execution loses depth.

Read the full checklist: 10 Red Flags When Hiring an Email Marketing Agency →

Questions to Ask Before Hiring an Email Marketing Agency

With the right questions, you can get into the depths of how the agency works. So, 

Strategy and approach

Ask how they develop your email strategy and what they prioritise in the first 30–60 days. 

Ask how they handle the transition from audit to execution.

Technical execution

Ask how they manage deliverability, what platforms they specialise in, and what their testing framework looks like. Answers here reveal whether they run systems or just send campaigns.

Team and process

Ask who specifically will work on your account, how many other clients that person manages, and how they collaborate with your internal team. Clarity here matters more than titles.

Performance and reporting

Ask how they measure success beyond revenue — what leading indicators they track, how they attribute email performance, and how they communicate when something is not working.

Logistics and communication

Ask about contract terms, how often you will connect, and what the approval process looks like. You should know exactly what to expect before you sign anything.

Logistics and communication

Ask about contract terms, how often you will connect, and what the approval process looks like. You should know exactly what to expect before you sign anything.

Clear answers matter more than perfect answers. You are looking for a healthy mix of structure and confidence.

Get the full list: 15 Questions to Ask Before Hiring an Email Agency →

How to Compare Agencies

Once you have shortlisted your choices, it’s possible that they all look the same to you. Same services and promises, even the tools. To select one from the list, you need to prioritise and compare, and see how each one will approach your business. 

Look for clarity in their recommendations. Strong agencies explain what they would change and why. The focus should be on measurable outcomes, not just well-designed emails.

What sets them apart?

Pay attention to how they handle strategy, execution and optimisation. Ask how they approach deliverability, how they use analytics and how they adapt when performance changes.

Deliverability matters more than most realise. Top agencies maintain 98%+ deliverability vs the industry average of 85–90%. That difference directly affects revenue.

Look at how deep their strategy goes. Strong agencies build around your business model and customer journey. Weaker ones rely on repeatable templates.

Pricing is also something you should consider. A lower-cost agency that delivers average results often costs more over time.

Focus on the value they create. The right partner improves performance in a way that justifies the investment.

Also, pay attention to how they communicate. Clear, consistent communication early on is usually a preview of how they will work with you.

See our full comparison: Best Email Marketing Agencies Compared →

Measuring Agency ROI

Return from email marketing builds gradually, and you see it in how performance improves month after month. 

First month is audit, setup, and fixing gaps. Then in months 2–3 it is optimisation and testing. By the 6th month compounding becomes visible – better segmentation, cleaner lists, automations that keep working without additional spend.

The math is simple. If your agency costs $5,000 a month and email revenue grows by $50,000, that is 10x ROI before compounding.

Like we mentioned above, email returns $36–$42 for every dollar spent industry-wide. A well-run program should hit that benchmark within two quarters.

What you track matters. Revenue is important, but it is not enough on its own. Look at how conversion rates change, how engagement holds over time and whether list quality improves. These signals usually show whether the system is getting stronger.

If three months in nothing is moving and your agency cannot explain why, that is your answer.

Read more – how to measure email marketing agency roi with a complete framework

Why InboxArmy?

Since 2016, we have worked with 5,000+ brands across 25+ industries, every engagement focused exclusively on email and SMS. That kind of specialisation, sustained over nearly a decade, builds a depth of pattern recognition that generalist teams simply don’t accumulate.

The team is 120+ specialists certified across 40+ ESPs. When your program needs a Klaviyo strategist, a Braze architect, or a deliverability expert, that person is already here — not hired for your account, but seasoned from working across hundreds like it.

Every account has a dedicated account manager – not one AM juggling dozens of clients. They are focused on thinking about your customer journey, your segmentation gaps, and your next 90 days.

The numbers below are what happens when that structure is applied consistently – 

Maven Lane (Premium Furniture)

Challenge? 

Maven Lane had strong products and a clear brand identity. Their email program had neither. No automations, a welcome sequence that failed to convert, abandoned carts recovering nothing, and designs that undercut the premium positioning they had built everywhere else. Email revenue at the start: $0.

Solution?

We built the entire program from scratch. Welcome series, cart abandonment, post-purchase flows, and regular broadcast campaigns around product launches, seasonal promotions, and flash sales. The welcome series led with bestsellers and brand values. Every template was rebuilt to match the brand’s visual identity and optimised for mobile.

Results?

• $700,000 in email revenue generated in 6 months
• Welcome series: $434,180
• Abandoned cart recovery: $163,433
• Single Labor Day broadcast: $52,930
• Average open rate across automations: 88.75%

“Inbox Army didn’t just do the work – they took the time to fully understand our brand, customers, and goals,” said Connell. “The strategic thinking behind their approach was what really made the difference.”

London Store (Fashion Ecommerce)

Challenge? 

London Store had been running email for 15 months with no real automations, text-heavy campaigns, and an ESP that couldn’t serve four markets from one platform. The channel was generating revenue, but nowhere close to what it should have been.

Solution?

We audited the full email operation, migrated them from Mailchimp to Klaviyo, and built dedicated Welcome and Cart Abandonment automations for each of their four markets. Dynamic content handled language and pricing by region automatically. Twelve emails a month, designed around imagery, with personalisation built around both purchase history and browse behaviour.

Results?

• 1,100% increase in email revenue over 9 months
• First month alone: revenue was 86% higher than the previous 15 months combined
• Automations drove 72% of all email revenue in month one
• Even in December (their busiest month), automations still accounted for 61% of total email revenue

“We looked at 16 different agencies, interviewed 8 of them, and selected InboxArmy as our number 1 pick.” – Barbara Puszkiewicz-Cimino, Associate Director at The Michael J. Fox Foundation. 

See all case studies →

“They’re responsive, proactive, flexible with shifting priorities, and genuinely invested in our business goals.” – Director of Marketing & E-Commerce, Sok-It

Ready to Talk Email Strategy?

If you’re looking for a team that can take ownership of your email marketing and improve how it performs over time, InboxArmy is built to do exactly that.

Schedule a free consultation →

FAQ

How much does it cost to hire an email marketing agency?

Before the number scares you off, here’s the context. Most agencies charge between $2,500 and $10,000+ per month. What you pay depends on scope and complexity. Think of it less as an expense and more as an investment in a channel that compounds over time.

How long before I see results?

You’ll likely see notice early improvements within the first 30-60 days. Additional profits in conversion and revenue show up only after over 60-90 days. 

What’s included in a full-service email marketing engagement?

Full-service agencies cover strategy, automation, copy, segmentation, and reporting. That’s standard. But scope varies by agency more than you’d think, so ask what’s actually included before you sign anything.

Can agencies help with both email and SMS?

Yes. Many email marketing agencies do. SMS and email tend to complement each other, so a lot of agencies manage both. It makes the customer journey more complete.

How do I know if an agency is a good fit?

They should ask smart questions about your business before they start pitching solutions. Full-service agencies cover more ground. But more channels usually result in less depth, and email is one of those areas where depth is very necessary.

What’s the difference between an email marketing agency and a full-service marketing agency?

An email marketing agency goes deep on email and automation. A full-service agency covers more channels, but it comes with a downfall. Their focus is spread thin across channels.

Should I hire a Klaviyo-certified agency?

Certification tells you they know the platform. It doesn’t tell you they can grow your business. What actually matters is whether they’ve done it before for brands like yours. Ask for real results, not just a badge.

What metrics should an email marketing agency track?

Revenue, conversion rates, click-throughs, and engagement. Be cautious of agencies that lead with open rates and send volume, those don’t pay the bills.

How do email marketing agencies improve deliverability?

Deliverability starts before you send a single email. First thing a good agency does is make sure SPF, DKIM, and DMARC are set up correctly. Then it’s about keeping the list healthy. That means removing disengaged subscribers through sunset flows, controlling how often you send so you’re not tripping spam filters, and staying on top of bounces before they snowball into a bigger problem. Elite agencies maintain 98%+ inbox placement rates, compared to the industry average of 85–90%. That 10–15 point gap translates directly into revenue.

What’s the typical contract length with an email marketing agency?

If your email marketing agency is working on a monthly retainer, then there is a 3-6 month initial commitment. It is long enough to build automations, run tests, and see meaningful results. Month-to-month contracts after that are reasonable to ask for. Be cautious of anyone demanding a 12-month commitment before you’ve seen any results.

Do I need an email marketing agency if I’m already using Klaviyo?

Yes. Most brands use less than 30% of Klaviyo’s capabilities without specialist support. The platform handles execution, and an agency brings the strategy and segmentation logic that turns those unused features into revenue.

How do email marketing agencies charge? Retainer or percentage of revenue?

Most use a monthly retainer. Some may include a pricing model based on performance and results.

Can an email marketing agency work with my existing design/brand team?

Yes. Email marketing agencies are used to working alongside internal teams to understand brand guidelines, content strategy, and the rest of it. If you choose the right one, they will blend right into your existing setup.

What happens if the email marketing agency doesn’t deliver results?

If email performance does not improve and there is no clear direction, it is best to reassess and consider switching.

How involved do I need to be with an email marketing agency?

You stay involved in approvals and direction. The agency handles execution, optimisation, and day-to-day management.

What size business should hire an email marketing agency?

Brands that generate $500,000+ annually tend to see the strongest returns. Below that, focus on getting core automations in place. Above $2M annually, a well-run program will be able to deliver 10–20x ROI through more advanced retention strategies. List size matters too – 5,000+ engaged subscribers give a meaningful base to work with.

Do email marketing agencies create email templates or use existing ones?

They do both. Agencies build new email templates or optimise existing ones based on performance needs.

How do email marketing agencies handle seasonality and promotions?

A good email marketing agency plans campaign strategies ahead of time. They align messaging with your business goals, and adjust based on performance trends.

Can I switch email marketing agencies mid-contract?

Yes, depending on the terms. Whatever the situation, remember that before you make the switch, you own everything – platform access, data, assets. 

What’s the biggest mistake brands make when hiring an email marketing agency?

Don’t choose an agency based on price alone. You may find a low-cost agency suitable for your needs. They may deliver the templates, but fall behind in strategy and planning. So, you end up with a busy campaign calendar and flat results. The other mistake is not asking hard questions during the sales process. If they can’t clearly explain their first 90 days, how they measure success, and who will actually be working on your account, that is a problem. That vagueness won’t go away even after you sign.