Email Service Providers Explained: The Ultimate Guide

What’s an email service provider (ESP)?

An email service provider is a tool that helps you create and send email campaigns to your subscribers. Some of the key features that distinguish ESPs from other email software are the ability to segment your audience, automate email campaigns, and analyze the results. That is why, for example, Gmail cannot be called an ESP — but we’ll get to that a bit later.

Can Gmail, Outlook, Yahoo Mail, and AOL be considered ESPs?

No. Apple Mail, Gmail, Outlook, and the rest are best reserved for internal communications within companies large and small. None of those have the functionality to be considered ESPs in the marketing sense. While you can use Gmail to send mass emails, you’ll have to do so with many limitations. You won’t be able to send more than 500 emails per day, nor will you have any segmentation, A/B testing, and analytics tools to speak of.

In short, these are email clients (or email services): good for personal use or office communications, but not for becoming email marketing tools in your kit.

Why are ESPs important? Why should I use one?

ESPs help you connect with your audience. Whether you are pursuing leads, promoting your products to existing subscribers, or simply sending transactional emails, an ESP gives you the flexibility you won’t have with a simple inbox provider. Plus, if you are bulk-sending emails from, say, a Gmail address, odds are they’ll be quickly flagged as spam. ESPs exist to ensure your email blasts are not going to waste.

Another important consideration is the arsenal of instruments ESPs provide for segmenting your audience, creating emails (with ready-made templates or HTML code), sending them, and analyzing the results. ESPs also give you the ability to create and automate email sequences  — whether promotional, informational, or transactional — so you won’t need a steady hand on the tiller at all times. They can ensure you send the right email to the right person at the right time.

Key features of email service providers

We’ve touched on some already — but let’s get into more detail.

Deliverability

Deliverability rates tell you how many of your emails reached your recipients. And not simply hit their inboxes, but avoid the spam folder in the process. Different campaigns you send can have different deliverability based on various factors including sender reputation, IP address, etc.

However, email service providers themselves have different deliverability rates as well. A good rule of thumb is to aim for a deliverability rate of over 90% when you are choosing an ESP. Carefully research your options and look at testimonials from small and big businesses alike that use the ESP you are considering.

Out of the limited platforms tested, these offered the highest deliverability in 2024: 

1. ActiveCampaign (93.4%)
2. MailerLite (92.7%)
3. Mailchimp (92.6%)

List management

The biggest component of this is audience segmentation. It’s common practice to segment your audience based on different criteria. These can be demographical (age, level of income, education, etc.), behavioral (based on page views, clicks, etc.), geographical, and more.

The short of it is, you create different segments based on who will find certain emails interesting — and then send these email campaigns only to subscribers who made the group. Naturally, you should be able to manage the email lists and segments using your ESP dashboard: create lists and segments, add or remove emails, track specific analytics, etc.

Email templates

These are meant to make your life easier when crafting emails, and there are two factors to consider: how big of a template library your ESP offers, and whether you can create and add your own templates if you so choose.

You can simply apply one of the ready-made templates before sending an email, but you need to upload your custom templates to the ESP first. So check how your shiny new ESP deals with importing HTML code.

Last but not least: look for ESPs that offer responsive email templates. By that, we mean ensuring your emails look equally good on desktop and mobile devices. A lot of people will open your emails from their smartphones — you should factor that in.

Email automation

Email automation ensures you can send entire campaigns automatically, without logging into the platform every time. Email automations are triggered by specific events, which ESPs allow you to define yourself.

For example, transactional emails can be triggered when a customer buys something, so they get their order confirmation in an email. Promotional emails can be set off when your potential buyer registers an account with you.

All you have to do is create one or a series of emails, define the events that trigger this or that email — and a good ESP will send them automatically.

A/B testing

One of the essential marketing tools is A/B testing — and that goes for email marketing as well. You will want to test how different versions of one email perform based on changes in email subject lines, layouts, CTAs, copy itself, etc. So choose an ESP that gives you the option to test how your (slightly) different emails perform.

Analytics and reporting

Naturally, there’s little point in crafting and sending an email campaign if you can’t tell how well it performed. That’s where the analytics dashboard comes in.

The key metrics you’ll want to track are open rates and click-through rates, i.e. how many people open your emails and how many click the links/CTAs inside. Other useful analytics include heat maps which show readers’ interactions with the email and unsubscribe rate — these will tell you where improvements can be made, both copy and design-wise.

And like we said, you’ll need these metrics for audience segments you create too, not simply for all of the emails you send. The overall picture has its uses, but the devil is usually in the details.

Integrations

Any ESP you choose will become part of your overall tech stack, so it’s important it plays well with your customer relationship management (CRM) and content management system (CMS). We’ve already mentioned how you might want to create custom templates — so also keep in mind the design tools your team uses.

How to choose an ESP?

Apart from functionality, there are technical and financial aspects to consider. These deserve our attention too.

User interface

Odds are at least your marketing team — and maybe your product team too — will be using the ESP. Choosing a technically complex solution that requires constant input from your developers will only slow your processes down. So you should go for an ESP that is easy to master and operate. Have mercy on your colleagues.

Support

At some point, you are bound to run into issues, so it’s crucial to know how quickly — and by which means — your new shiny ESP can help out. These platforms can have tutorials, guides, and FAQs on their website; while online chats, email communication, and phone calls exist if you’d rather talk to a person.

Check which options are available to you and try to find out how quickly support agents respond to issues. To that end, go through reviews and testimonials about ESPs.

Security

There are three main factors here to consider:

• Data encryption: the best type is end-to-end encryption. It means the data you send is encrypted during both the sending and the receiving process, making it impossible for third parties to decipher.
• Two-factor authentication: you can add another layer of security on top of the standard login-password combination. It can be a code that keeps updating or biometric data.
• Alias address: that’s an address you can share with third parties if you don’t want them to know your actual email. Once they send something to your alias address, the message will automatically pop up in your actual inbox — with the sender none the wiser.

Keep in mind the data you collect about your customers — and use to segment them into lists — most likely falls under GDPR requirements. Some ESPs specifically mention that they comply with these and ensure data protection via encryption.

Pricing and scalability

Pricing will depend on one of two factors: the number of emails you send, or the number of subscribers you have. First and foremost, do not start with a pricing plan that you’re sure to exceed in the near future: give yourself some breathing room.

Secondly, explore which plans exist and factor in how your business is going to grow. Switching ESPs can be a pain, so when you settle on one, try to stick with it for as long as it meets your requirements.

Finally, keep in mind that most popular ESPs provide enterprise plans — these have custom pricing depending on your specific business needs. Enterprise plans exist to cover companies whose subscriber list and/or the volume of the emails they send simply doesn’t fit into simpler plans.

However, it’s probably not the best idea to start with an enterprise plan right away: you won’t have much room to scale. Unless your email marketing channel is so huge that no ESPs can offer you anything other than enterprise, start smaller.

Best email service providers

There are a lot of options on the market — we are going to go over the best ones below.

Selzy

Selzy allows you to start creating and sending emails within 15 minutes — the learning curve is not steep at all. If you have no more than 100 contacts and are sending under 1,500 emails a month, you can use the free version, just to test things out. 

The free plan won’t allow you to try more advanced features, such as segmentation and A/B testing, though. That’s why other plans exist. Pricing starts from $5.25 per month (billed annually) for 500 subscribers and unlimited emails. On the cheapest Lite plan, you’ll also get the shareable email URLs.

Naturally, Selzy offers a variety of ready-made templates to choose from, an AI email builder to generate your own, and integrations with your favorite CRMs such as Zoho and Salesforce.

Mailchimp

Mailchimp has a standard toolkit, but they place an emphasis on one thing they do particularly well: help you create tailored customer journeys. They boast a 7x increase in orders and a 2x increase in click rates — if you rely on their Journey Builder tool. 

Other Mailchimp features are pretty classic: audience segmentation tools, analytics, AI assistance when crafting emails, etc.

Mailchimp’s pricing can be a sore point, though. For 500 subscribers, the Essentials plan is $13 per month; the Standard is $20 (both have a 50% discount on the first year though, so it’s $6.5 and $10 respectively). There’s a free plan but you’ll be limited to 500 contacts and very basic features.

Constant Contact

Constant Contact positions itself as a tool for small businesses — or big ones who are opening branches in new locations and need to attract new customers. They boast a 97% deliverability rate — and assure you their customer support will help solve your issue.

Other features they offer are pretty standard, such as a big template library (200+) templates, AI assistance with copywriting and design, and integrations with different CRMs.

Constant Contact doesn’t have a free plan, but there is a 30-day free trial on offer. For 500 subscribers, you’ll pay $12 per month for up to 5,000 emails for Lite, while the Standard plan will set you back $35 for up to 6,000 monthly emails.

Campaign Monitor

Campaign Monitor has a pretty standard features pack — but they do throw in several interesting nuggets. We especially liked how they create custom email templates that fit your brand: all you need is input your site’s URL. Another interesting feature is the countdown timer you can insert in your emails to create urgency.

Oh, there are also lead capture forms Campaign Monitor offers: from a simple email signup button to an entire landing page branded to fit your style.

Pricing starts with the Lite plan — which is $12 per month with 2,500 email sends; the Essentials plan is $29 per month with unlimited emails. There’s also a 30-day free trial, however, you won’t be able to use more advanced features (such as AI writing assistance) during this period.

Kit

We couldn’t just pass it by. Kit (formerly known as ConvertKit) is behind many creators you know: James Clear, Ryan Holiday, Nisha Vora, and Rachel Rodgers are among those.

Kit is business-oriented and their website is littered with cases of creators growing their audience and revenue with Kit’s help. Features are almost secondary, but you get the usual package: automations, audience segmentation, free migration from other platforms (if your base exceeds 5,000 subscribers) — and integrations.

There’s a free plan you can use if your base is under 10,000 subscribers and you’ll get unlimited emails, but you’ll only get one automation and it’s for one user only. The next step — the Creator plan — will set you back $15 per month for 300 subscribers and unlimited emails and will let you create as many automations as you want.

We’ve covered other email marketing services in detail too. Feel free to take a peek for a deeper dive into possible options.

Wrapping up

An email service provider helps you connect with your audience on a massive scale. If you have a big customer base, an email service provider will surely make your life easier by allowing you to automate email sending, segment your audience based on preferences, personalize your content, and analyze the results of your campaigns.

Other features you should look for in an ESP include a library of templates, the ability to A/B test your emails, integrations with your CRM and CMS — and of course a good deliverability rate.

You should also think about your marketing team when choosing an ESP. Aim for a provider with a user-friendly interface, lively support team, robust security, and flexible pricing with multiple plans. We hope we’ve given you enough info to go on.