What is an Email API: Comprehensive Guide

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Written By Tyler Harz

With a whopping 4.26 billion email users in 2022, expected to hit 4.73 billion by 2026, it’s clear that email is a big deal for business communication and marketing.

But, getting your emails in front of your customer’s eyes isn’t as simple as it used to be. That’s where Email APIs come into play, working behind the scenes to make email communication smoother and automated.

Email APIs can handle transactional emails, marketing blasts, and the reception and processing of incoming emails. They come packed with features like customizable email templates, detailed email analytics, and robust error handling. Whether you’re looking to improve open rates, handle authentication, and compliance, or just boost your email marketing campaigns, an Email API service is often the way to go.

In this article, we’ll explore what Email APIs are, compare them with SMTP, and look into various types of Email APIs. We’ll also touch on a few of our favorite Email APIs. By the end, you’ll have a solid understanding of Email APIs and be ready to leverage their benefits in your digital strategies. Let’s get started!

What is Email API?

Email API, short for “application programming interface,” serves as a conduit, bridging various applications or systems with email delivery services. At its core, it’s a set of rules that allows different software entities to communicate with each other. Through Email APIs, developers can find a structured way to access the functionality behind email delivery platforms, such as sending, receiving, and storing emails.

Understanding the mechanics behind Email APIs gives us a look into what an incredible feat modern communication actually is: when a web application wishes to send an email, it crafts a request in a manner the Email API can comprehend. This request is then dispatched over the internet to the email service, which processes the request and executes the action—be it sending, receiving, or any other email-related task. 

Employing Email APIs offers a number of advantages. It paves the way for automation, where routine email tasks are handled with little to no human intervention. This not only accelerates email processing but also minimizes the likelihood of errors. Moreover, it allows for a heightened level of customization. 

Emails can be tailored to a fine degree so that your communication is not only effective but also aligns well with your brand’s identity. Plus, the analytics provided through many Email API providers empower organizations to continually refine their email strategies and optimize for better engagement, open rates, and results.

Email API vs. SMTP: A Comparative Analysis

At the heart of email communication lies SMTP, or Simple Mail Transfer Protocol, a standard protocol at the center of email transmission across IP networks. SMTP’s primary function revolves around directing email along the right pathways from sender to recipient. It’s an old yet trusted method, having been the backbone of email communication since the 1980s.

When it comes to comparing Email API and SMTP, there are plenty of differences. SMTP, being a protocol, follows a strict set of rules for email transmission, whereas Email API, a more modern concoction, provides a broader suite of tools, enveloping not just sending but also receiving and organizing emails. 

The contrast in their operation is stark—SMTP follows a rigid path, while Email APIs offer a more flexible, programmatic approach to email management. 

Let’s illustrate this with an example. Consider a scenario where your business needs to send transactional emails, manage incoming customer inquiries, or analyze the performance of email campaigns. If you rely solely on SMTP, you would have to integrate with an SMTP server for sending emails and then devise additional solutions for receiving emails and analyzing data.

Now, if you use an Email API instead, you can not only facilitate the sending of emails but also the reception and organization of incoming emails. Plus, these APIs often come with built-in analytics tools to give you insights into email performance, delivery rates, and engagement metrics. Long story short—they are just plain easier.

Pros and Cons of Email APIs vs. SMTP

Email API Pros

  • High programmatic control allows for better integration and automation.
  • High degree of customization in email content, styling, and delivery options.
  • Facilitates the automation of email workflows.
  • Built-in analytics and tracking features for better insight into email performance.
  • Robust error handling with detailed error messages aiding in troubleshooting.

Email API Cons

  • May require a learning curve for individuals unfamiliar with APIs.
  • Could be overkill for simple email-sending tasks.
  • Might be more expensive depending on the provider and usage.


  • Simplicity in setup and usage for basic email-sending tasks.
  • Proven reliability for email delivery over decades.
  • Generally lower cost or free with basic email services.
  • No need for additional learning for individuals familiar with email servers.
  • Supports basic email delivery across various platforms and systems.


  • Limited to basic email sending unless paired with additional tools.
  • Lacks native analytics and tracking features.
  • Limited error-handling capabilities make troubleshooting more challenging.
  • Less programmatic control and customization.
  • Automation requires external tools and can be more complex to set up.

Exploring the Varieties: Types of Email API

There are a few different types of Email APIs, and deciding which one to use comes down to what you want to get out of it. Are you sending emails and need to automate the process as much as possible? Or is the work mostly revolving around receiving emails? Do you need verification services or barebones? 

These are some questions to keep in mind when considering the different types of Email APIs. Let’s look at some of the common terminology and different varieties you’ll find.


SMTP lays down the rules of engagement for sending and receiving emails on the internet. SMTP APIs take this a step further by offering a programmatic interface to interact with email servers and services. They are instrumental in:

  • Sending automated emails such as transactional notifications or marketing blasts.
  • Receiving and parsing emails to extract valuable data.
  • Managing email lists including subscribing, unsubscribing, and segmenting email addresses.

SMTP is also easier to migrate and easier to set up. For instance, applications unable to integrate with REST APIs, perhaps due to being legacy applications or third-party custom solutions, may find SMTP APIs to be their ally in email sending. 

However, it’s noteworthy that SMTP can be slower due to more server interactions, making REST APIs a preferable choice when possible. Let’s talk about them next.


REST, short for Representational State Transfer, is a set of standards dictating how an API should function. REST Email APIs expose endpoints accessible via network requests like GET or POST, often secured by an API key for authentication.

  • Email Validation: They could serve as email validation APIs, ensuring the email addresses are valid before any communication is sent.
  • Sending Email Campaigns: They can handle the sending of email campaigns and transactional emails.
  • Accessing Email Data: They might provide access to email data for a particular email client.

Since REST APIs extend to handling a variety of email-related tasks, their simplicity in integration and faster performance as compared to SMTP make them a highly favored choice.

Transactional vs. Contextual Email APIs

Transactional APIs are the workhorses for businesses needing to dispatch a large volume of emails with minimal customization, ideal for automated marketing updates, promotional offers, and transactional notifications. In short, these are the simple solutions when you just want to focus on the communication itself.

Contextual APIs cater to more personalized, conversation-driven email interactions like sales outreach, customer service inquiries, and tailored newsletters, enriching engagement by allowing customization and analytics tracking. When you want a more complete solution embedded directly into your app, a contextual API is the way to go.

Sending vs. Receiving vs. Validation

When you’re deciding what exactly you are using the API for, you’ll probably see plenty of discussion encompassing Sending, Receiving, and Validation APIs.

Sending APIs are behind automating and customizing email messages to align with your business requirements. These are typically transactional in nature, like notifications, email campaigns, or any other form of marketing communication. 

On the flip side, Receiving APIs simplifies the process of receiving emails from customers, partners, or other stakeholders. They act as a funnel—channeling incoming emails to the appropriate destinations without manual intervention. If you’re collecting leads for sales and marketing purposes, you’ll make use of this type of API.

The accuracy of email addresses is fundamental for successful email communication, and this is where Validation APIs shine. They scrutinize email addresses for correctness and authenticity before any communication is dispatched. As a result, they help to increase your deliverability rates, which is important in any use.

Top 4 Best Email APIs

Okay, so you have an understanding of how Email APIs work and a few of the most common types. But the market is saturated with different services, all promising the world. So, how do you figure out the best Email API for your needs? We’ve checked out quite a few and compiled the top 4 Email APIs below.

1. AbstractAPII z3Mvmug8bUG9CoFD9y 77UJgDSAEpPhXLQ9GRkuMTuaiEWQlOAwCecNS0jNCtgK6yl6NW9E6J Div Nuko5D6XNffuuzRhQt5B3UBGEOUZNsqEm2W0S2SL9u

Abstract’s Email Verification and Validation API provides real-time checks for email validity, typo correction, and identification of disposable/free email providers, all while being privacy-friendly. 

One of the most important things to keep in mind when sending emails for business is whether or not those emails are actually getting into inboxes. Real-time MX & SMTP checks help make sure email servers are set up right and ready for your emails. They can catch problems early, so your emails don’t bounce back or land in spam folders.

Another standout feature is its typo checking and smart suggestions to autocorrect email input errors. Aside from that, you also get plenty of integration capabilities, if you want to use it with your CRM or tie in with your marketing workflows. 

If you want to get started with it, their pricing system is pretty generous, and you can tell exactly how much you’ll pay based on the number of requests per month. The API is free for 100 requests per month, with paid plans starting at $9/month for 5,000 requests. 

2. NylasJhJSY8jSXJvNDiN3FY6M BMEvOhrcDBcM aXskkWChr3hczVFkhS7uRiPTafqWFs2AgRa5xXHzYQWAexs8dlnivu7TqMXq5FmjURHwrjuDGhBOzDD7K9arVjLrWOxvWTajFNBwfL R3t foj27N8ipA

The Nylas Email API is a universal bridge between your app and users’ inboxes, boasting a 99.6% deliverability rate. Its standout feature is its universal compatibility with all email service providers without requiring custom code—a huge time and money saver. 

The API supports full Create, Read, Update, Delete (CRUD) capabilities on a fairly scalable platform, with a focus on enhancing user engagement and ensuring enterprise-grade security. 

While praised for its developer-friendly nature and high deliverability, it could present a learning curve for newcomers to email APIs. Not to mention, your cost could escalate based on usage or if higher compliance and advanced features are something you need. 

As for how much those costs are, Nylas offers a pretty flexible pricing model. You get a free tier for testing, a pay-as-you-go option, and custom plans for larger organizations, segmented into Entry, Core, and Plus packages depending on what you need​.

3. MailerSendB TP5Ue G

MailerSend caters to developers and non-technical teams alike, offering a platform for handling transactional emails with ease. The extensive support documentation is a highlight, making it easy for you or your developers to get up and running.

One of the attractive features of MailerSend is its pricing structure which begins with a free tier, allowing you to send up to 12,000 emails per month at no cost. For those with higher email-sending needs, it transitions to a pay-as-you-go model, which can be cost-effective, especially for growing businesses. 

G2 reviews affirm that MailerSend is super easy to use, and responsive customer support is a major strong point. The platform’s usability and integrations have also been praised by users, even though MailerSend is relatively new in the transactional email space. These attributes make it a solid choice for organizations looking to streamline their email communication processes without a hefty price tag.

4. MailGun

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MailGun is a go-to for developers keen on managing bulk emails through an API. It simplifies email tracking and sending, offering a RESTful API that plays well with various programming languages like Python, Java, and Ruby. 

The main advantage of using MailGun is its ability to handle email sending via its SMTP servers, instead of relying on your own hosting plan. This leads to emails that are more trusted, get marked as spam less often, and have a higher delivery rate. Additionally, MailGun has built-in features like logging and automatic retries.

While it excels in deliverability and scalability, it’s not quite cut out for the non-tech savvy due to its developer-centric design. The good news is that there is extensive documentation if you feel like taking the plunge.

There is a free tier for you to try it out, with up to 5,000 emails a month. After that, pricing kicks off at $35 monthly, scaling up to $80 or $90 for more advanced plans

Conclusion: Understanding Email APIs

Email APIs are designed to remove the hassle of automating your email communications, so you can zero in on your core business objectives. The right ones can automate routine email tasks and offer a platform for more straightforward email management. But wasting time on something complex and unintuitive will take your mind off of more important things.

Rather than getting caught up in the complexities of email handling, leveraging an Email API should streamline your processes The goal is to get your app up and running as quickly as possible, without getting lost over common stumbling blocks. 

But opting for the wrong Email API can be a costly choice that can set back your business operations. A few things to remember when you’re trying to decide on which Email API to use:

  • Look for an Email API that easily integrates with your existing systems and has SDKs or libraries in your technology stack.
  • Opt for providers that offer a sliding scale or pay-as-you-go option to ensure cost-effectiveness as your email volume grows.
  • Check reviews and ask for recommendations to gauge the reliability and performance of the Email API.
  • Ensure the Email API provider complies with necessary data protection regulations and has robust security measures in place.
  • Besides picking something that is easy to use and boasts thorough documentation, you should also aim for something scalable. This way, when your demand increases, you can be ready.

Frequently Asked Questions

How does an Email API work?

Email APIs work by providing a set of rules and protocols that allow applications to send, receive, and manage emails programmatically through network requests.

What is the difference between Email API and SMTP?

Email APIs provide a programmatic interface with more customization, automation, and analytics, while SMTP is a basic protocol for sending emails with limited customization and analytics.

Why should one use an Email API instead of SMTP?

Email API offers better customization, automation, analytics tracking, and often more robust error handling compared to SMTP, enhancing email management and engagement tracking.

What are the different types of Email APIs available?

Types include SMTP APIs, REST APIs, Sending, Receiving, and Validation APIs, and Transactional and Contextual APIs, each catering to different email communication needs.

How do Email Sending APIs improve email delivery?

This is actually one of their biggest use cases. Email Sending APIs improve delivery through better customization and automated workflows, and often have built-in features to manage email deliverability and reduce bounce rates.

Are Email APIs secure for sending sensitive information?

Email APIs can be secure when using HTTPS and authentication mechanisms like API keys or OAuth, but be sure to choose a reputable provider with strong security measures. Read the API documentation for whichever one you end up using so you can be sure that you’re staying as secure as possible.

Can Email APIs integrate with other applications and systems?

Yes, Email APIs are designed to integrate with various applications and systems, so you can automate email communication within different software environments, such as your CRM or marketing programs.

What are the limitations of using SMTP for sending emails?

SMTP has limited customization, lacks native email analytics, and can be slower and less efficient in handling large volumes of emails compared to Email APIs.

How to choose the right Email API for your business?

Consider your email volume, need for customization, automation, analytics, budget, and the reputation and security measures of the Email API provider.

Are there any free Email APIs available?

Yes, some providers offer free tiers or trial periods for their Email APIs. Many services like Abstract API, Nylas, MailerSend, and MailGun offer basic free versions to get started. Depending on your expected use cases, you might need more than a free provider can offer. But testing your web app and email campaigns on a free plan first will help you avoid expensive mistakes. Once you build up your email list and start getting more volume, then you can scale up easily.

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