September 22, 2021

What is an Email Marketing API and Why Should You Use One?

Reading time about 8 min

Whether you’re building a software application that needs to send out emails, an ecommerce site that sends transactional messages to customers, or an automated performance report, using an email marketing API is absolutely essential.

Email remains one of the most effective and direct forms of communication for businesses to interact with customers.

Thanks to the help of email marketing service providers like Brevo, businesses are able to send bulk email campaigns to large groups of contacts and scale their one-to-one email messages to handle any volume without having to worry about email deliverability issues or setting up their own SMTP server.

While online email marketing applications are great for designing and sending emails, sometimes businesses have more complex use cases for email that require the services of an email marketing platform to be directly integrated into a website or application’s functionality. This requires the use of an email marketing API.

What is an API?

For those of you who aren’t familiar with the term API, it stands for “Application Programming Interface,” and it simply refers to the set of methods by which developers can access the different functionalities of a software application using code rather than logging into the application.

To illustrate this in a clearer way, let’s use an analogy: think of a software tool like a restaurant. Most people who want to eat at a restaurant go to the establishment, sit down at a table, and order food off the menu from a waiter. These “normal” customers are similar to software users who log into an application and make use of the features in the tool by clicking around in the normal graphical user interface (GUI).

But, what if you want have that food delivered to you rather than going all the way there, sitting down at a table, and ordering it from a waiter? In this case, you’ll probably call into the restaurant and place an order for delivery. This is like using a software tools’ API. You still have access to the items on the menu, but you have to order them through a different process and they are delivered directly to you rather than you having to go to the restaurant.

APIs let a user “log in” to the application by sending a programmatic request using an API key (usually just a random encrypted string of characters) that is unique to their account for authentication. The API requests give developers access to the different features of the platform using the methods and endpoints (request URIs that allow access to different features or data objects offered through the API) that are provided in that particular software’s API documentation.

View the Brevo API documentation

Common Email Marketing API Use Cases

Now that you have a better understanding of what and API is, and more particularly what an email marketing API is, let’s discuss how an email API can be used to help businesses grow and develop better customer relationships.

Power application notifications and transactional messages

Probably the most common reason that businesses will use an email marketing API is to programmatically add email notifications and transactional messages to their website or software tool.


Many software tools and websites use notifications to inform users when something happens with their account on the platform. In social media tools like Facebook or Instagram, this could be a new comment or “like” on a post that a user made.

It doesn’t always make sense to send an email for each action that occurs in an application. However, if it’s an action that is more important or time-sensitive and requires the user’s attention, sending an email can be a great mechanism to ensure that the user sees the information in a timely manner.

For an excellent example of how email notifications are built into an application, take a look at the email from Airbnb below:


This email is sent automatically by Airbnb’s website using an email marketing API to remind the user of an upcoming reservation that they made on the platform.

Of course, if you only have one or two customers, it would be possible to send this email manually by logging into an email marketing platform. But to achieve any kind of scale, they require an integration using an email API.

Transactional Messages

If you’ve ever shopped online or made in-app purchases, then you’re probably familiar with transactional emails. These are messages that communicate timely information that is usually related to a specific transaction the user makes on a website or application. The most common example would be an order receipt.

Email marketing APIs let you design beautiful transactional emails and integrate them directly into the functionality of your website so you can get the full potential of a well-designed email instead of just including the bare essential information for customers.

limebike receipt transactional email

LimeBike uses an email marketing API to send transactional email receipts when funds are added, while also including the customer’s referral code and a nice HTML design.

Sometimes email marketing platforms will offer plugins for the most popular eCommerce CMS systems that make it easier to customize transactional messages without needing the API. For example, Brevo has powerful integrations with WooCommerce, Shopify, and WordPress. But, if you’re using a less common eCommerce system, or you’re building a software tool from scratch, your transactional messages can still be customized through an email marketing API.

Customize your activation and growth hacking workflows

Emails can also be useful for boosting engagement with your growth hacking or product engagement workflows. For example, you might want to send an email reminding users to leave a review about a specific product that they purchased. This can be done using an email marketing API to send the message at the most opportune moment so you can generate more engagement and give other customers useful product information.

Yelp Review Email

You can see in the example above how Yelp uses an email marketing API to send out an HTML-designed email that contains dynamic information specific that the user in order to encourage more reviews (improving the core value of their app).

If you rely on specific webhooks on your website or in emails to automate your lead nurturing workflows, you can also use an email API to automate this programmatically.

This leads us to our next point on the list:

Connect other software tools to your email marketing

APIs exist so that developers can connect the functionality of one tool to another. So in addition to connecting your email marketing tool to software or websites that you create, you can also use an email marketing API to connect it with other tools that you use.

Two of the most common types of tools that you could connect are CMS and CRM systems:

  • CMS: If you use a CMS to publish content on your website, you can use an email marketing API to automatically send your email contacts an email whenever you make a new post on your site.
  • CRM: You can use an email marketing API to automatically sync your email contacts with your CRM tool or set up triggers when contacts meet certain criteria in your CRM to automatically send them emails that you designed in your email marketing platform.

These are just two examples, but if you are using a tool that has an API and you can think of a way that email fits with it, you can programmatically connect it to your email marketing just like that through the API.

Create custom dashboards and reporting tools

In addition to sending emails and syncing contact information, email marketing APIs also let you access email performance statistics. This is helpful if you want to create custom email marketing dashboards or automatically integrate email marketing data into your other marketing reports without having to manually export data from your email marketing platform.


There are many different reasons why someone should use and email marketing API, which is why it’s important to understand what the capabilities are for using one. But, one thing you should always keep in mind when choosing between different email marketing API providers is scalability.

You never want to left out in the cold when your business achieves rapid growth and the email API solution you used to integrate with your business can’t keep up (or worse, the price scales beyond what you can afford).

If you’re a website owner or developer looking for an email marketing API that will effectively scale to any volume while keeping a reasonable price tag, check out Brevo.

Test-drive Brevo’s transactional email service

Free SMTP server for up to 300 emails/day, email API for developers, transactional email templates, and unlimited log retention.

Open my free Brevo account now >>

To learn more about the methods and endpoints available through the Brevo API, just take a look at our API documentation.

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