If you're short on time and need to make a quick decision, my top pick for email validation is AbstractAPI. For a robust email marketing tool, Mailgun and SendGrid are great options, while Amazon SES is ideal for those already using AWS services. If you're looking for fast inbox placement, Postmark and SparkPost (MessageBird) are solid choices, while Twilio SendGrid is a reliable option for those already using Twilio for other communication integrations.

Email APIs at a Glance

  • AbstractAPI: Best for freelancers, small businesses, and anyone who needs to integrate an email validation service into their app.
  • Mailgun: Best for enterprise businesses who need an API to handle email marketing and want a service with reliable email deliverability.
  • SendGrid: Best for small business email (free plan) and enterprise teams.
  • Amazon SES: Best for those already using AWS services like EC2 or Elastic Beanstalk.
  • Postmark: Best for small businesses and freelancers or those looking to get started with email sending.
  • SparkPost (MessageBird): Best for people just starting out all the way through enterprise companies.
  • Twilio: Best for businesses already using Twilio for other communication integrations.

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What is an Email API?

API stands for Application Programming Interface. An API is a set of methods and protocols for interfacing two separate pieces of software. These days, the term "API" most commonly refers to a set of online tools that can be accessed via network requests to perform simple tasks that developers would otherwise have to code themselves.

An email API service allows developers to access functions and data useful for handling email. For example, an email API might offer a set of methods for sending and receiving emails from your application, or it could be an email verification API that validates the addresses of incoming emails to remove invalid email addresses.

The primary benefit of using an email API service rather than rolling your own SMTP server or writing email validation code is that you offload the effort of these tasks to a dedicated service that will most likely do them faster and better than you can. You also save space in your own codebase and remove the need for ongoing maintenance of that code.

Key Takeaways

  • An email API service lets developers connect an application to an email service provider and use functionality without having to build it themselves.
  • An email API can also handle the validation and verification of email addresses
  • An email API removes the burden of code creation and maintenance
  • Because an email API is dedicated to one specific task, it usually does it better and faster than a custom piece of code written by a developer could

Types of Email APIs

There are different types of email API services that do different things (some handle sending and receiving while others handle validation, for example.)


REST stands for Representational State Transfer. It is a set of standards that govern how an API should operate. A REST API exposes an endpoint that developers can access through a network request like a GET or POST request.

REST API calls are usually secured by an API key, which authenticates the developer to the API and allows them to make requests. Depending on the API, it may be an HTTP API or an HTTPS API. HTTPS is more secure as network requests are encrypted.

When you make API calls to a REST API, the API receives the request, performs some task (like validating a provided email address), and returns a standard HTTP response to let you know whether or not the task was successful.

A REST email API could do one of many things. It may be an email validation API, or it might handle sending email campaigns and transactional emails, or give you access to email data for a particular email client.


SMTP stands for Simple Mail Transfer Protocol, and it is the set of rules that govern how emails are sent and received on the Internet. In order to send emails from an application, it is necessary to use an SMTP server.

Some services offer both API and SMTP sending. SMTP sending means integrating with an SMTP server and using those ports and protocols instead of regular REST API calls. Applications that can't integrate with an API (some legacy applications or third-party-built custom solutions) may need to use SMTP to send emails rather than a REST API.

The only downside to using SMTP vs a REST API to send emails is that SMTP can be slower because there is more back and forth between the servers. We recommend choosing a REST API whenever possible as it is simpler to integrate and faster.

Receiving vs Sending vs Validation

Many email API services do a few different things, but it's up to you to decide what you need the API for. If you need an email delivery service to send emails from your application, you'll need to look for an API that handles SMTP. If all you need to do is verify email addresses, look for that. Some APIs may do both.

Other types of Email APIs

In addition to sending, receiving, and validation, email APIs may also track transactional emails, send marketing emails and email campaigns, allow users to create temporary email addresses, handle bulk validation of an email list, and more. You will need to research the specific features of any API you are considering before making your choice.

Features to Look for in an Email API

Email Delivery and Reliability

If what you need is to send emails from your application, make sure the API you pick has a good sender reputation and a history of reliability when it comes to delivering emails. Email deliverability is influenced by many factors, including bounce rate, number of spam complaints, email content, and how easy it is for users to opt-out if they want to.

Make sure the SMTP API you choose has a solid sender reputation and email deliverability score.

Customization Options

How easy is it to get exactly the features you need (and pay for only those features) from your chosen API? Sure, the API may handle validation and SMTP and verification, and transactional emails, but do you really need all that?

Make sure you can customize the plan you choose to fit your needs. For enterprise clients, most companies provide flexible plans that can be tailored to do exactly what you want.

Analytics and Reporting

This is an often-overlooked aspect of choosing an API, but it is one of the most crucial. If you can't track analytics and get detailed logs about how your emails are being sent, you won't know how your emails are performing and what to improve about your process.

Not only that, the API should return standard error and success messages so that developers can quickly debug issues when things go wrong, or show messages to users if need be.

Integration Options

Does the API provide client libraries for the most popular programming languages? Does it restrict how you can access its features? Will it integrate email functionality seamlessly into your application?

Most APIs - particularly REST APIs - are language agnostic and return data responses as either JSON or XML. This makes them flexible and easy to work with.

Security Features

Is the API secured with an API key? Does it use HTTPS? What other security and privacy features are in place to ensure the safety of your users' data? Email is incredibly sensitive information and should be handled with care.

The Top 7 Best Email APIs

Here's a quick overview of some of the most popular email API services. Some of these are email validation API services, while others handle sending and receiving email campaigns.


The AbstractAPI Free Email API is an email validation service that handles one-off and bulk verification of email addresses. It's a simple REST API secured by an API key that exposes an endpoint to which you can send email addresses for verification.

The API returns a JSON response with information about the provided email address, including deliverability, whether it is a disposable email address, temporary email address or inactive address, whether the MX records are up to date, whether the address appears on known spam lists or other blacklists, and more.

You can use this email verifier API to validate email addresses when users sign up to your mailing list via a form on your website. This prevents invalid email addresses from ever making it onto your list or into your marketing campaigns.

The API also offers a bulk validation option where you can upload a CSV file of email addresses for validation. This is a necessary task to perform at regular intervals to keep your mailing list clean and healthy.

There is a free version of the API that allows you to make up to 100 requests at 1 request per second. From there, plans start at $9/month for up 5000 requests per month.

Price: Free for 100 requests. $9/month for 5000 requests, $49/month for 50,000 requests, $99/month for 100,000 requests

Best for: freelance developers, small businesses, and anyone who needs to integrate an email validation service into their app


Probably one of the best-known email APIs around, the Mailgun API is a powerful email marketing tool that allows you to send emails from your application, and also track those emails and get advanced email analytics and metrics. It is built on Google with 99.99% uptime, and is SOC I & II certified, GDPR, HIPAA, and ISO 27001 compliant.

The API provides client libraries for Ruby, Node, Python, .NET, PHP, and Java. It offers several layers of authentication to protect your sender reputation and prevent bad actors from impersonating your account, including sending with SPF, DKIM, and DMARC protocols.

Through their Mailjet integration, Mailgun also offers the ability for teams to create email templates using a handy drag-and-drop editor. These templated emails can then integrate email functionality and analytic tracking seamlessly through the API.

You can get started with the Mailgun API for free. The free plan is a 1-month trial and allows you up to 5000 emails. From there, plans start at $35/month.

Price: Free to send up to 5000 emails for 1 month. $35/month for 50,000 emails, $90/month for 100,000 emails, custom plans available on request

Best for: enterprise businesses who need an API to handle email marketing and want a service with reliable email deliverability.


Like Mailgun, SendGrid offers a robust and reliable transactional email API and one of the best email sending APIs. The platform is used by companies like Uber, Spotify, AirBnb, and Yelp to handle marketing emails, transactional emails, email validation, email templates, email tracking, and more.

Libraries are available for Python, Java, C-Sharp, PHP, and Node. There are both REST and SMTP integrations available, and interactive documentation makes getting up and running very easy.

SendGrid offers SPF records, custom DKIM, and dedicated IP addresses. They can provide consultation from delivery experts on M3AAWG, ESPC, DMA, and EEC. They have partnerships with mailbox providers like Gmail, Microsoft, and Verizon.

// using Twilio SendGrid's v3 Node.js Library
// https://github.com/sendgrid/sendgrid-nodejs
const sgMail = require('@sendgrid/mail');
const msg = {
  to: 'test@example.com',
  from: 'test@example.com',
  subject: 'Sending with Twilio SendGrid is Fun',
  text: 'and easy to do anywhere, even with Node.js',
  html: 'and easy to do anywhere, even with Node.js',

You can use SendGrid free for life to send up to 100 emails per day. The free plan does not offer email validation, dedicated IPs or SSO, but otherwise is very generous. Paid tiers start at $19.95/month.

Price: Free for life to send 100 emails/day, $19.95/month for 50,000 emails $89.95/month for 1.5 million+ emails, custom plans also available.

Best for: small business email (free plan), enterprise teams

Amazon SES

Amazon SES stands for Simple Email Service. It is an AWS integration that handles email sending and receiving. It allows you to automate transactional emails and marketing emails, send automated notifications, and track results.

SES is HIPAA-eligible and FedRAMP-, GDPR-, and ISO-certified. It is trusted by Amazon, Netflix, DuoLingo, and Reddit. Because it is part of AWS it is very easy to implement for companies already using other AWS services like EC2, S3, or Aurora.

SES is a highly reputable service that allows you to send as a trusted sender with many layers of authentication. It integrates seamlessly and allows you to configure sending options without coding. Because it is part of AWS it comes with training and extensive documentation.

You can get started for free - Amazon offers 62,000 outbound messages per month when you call Amazon SES from an Amazon EC2 instance directly or through AWS Elastic Beanstalk. SES is priced with bulk sending in mind, so after the free tier, you pay per email and only pay for what you send.

Price: Free for up to 62,000 emails/month when used directly from EC2 or EB, $0.10 per 1000 emails over 62,000 or not sent from EC2, $0.12 per GB of attachments sent

Best for: Those already using AWS services like EC2 or Elastic Beanstalk


Postmark is a great alternative to the Mailgun API and SendGrid. They have an excellent time to inbox score at just 5 seconds for Gmail and Hotmail and 97 seconds for Apple Mail. They handle sending and receiving as well as email tracking, templates, and transactional emails.

Postmark is GDPR-compliant and offers support at every tier. They offer both API and SMTP sending, which is great for companies dealing with legacy code that requires SMTP sending. There are client libraries for all major languages, as well as migration guides for switching from other popular email API services.

You can use Postmark free for life - the free plan includes access to all features and up to 100 email sends per month. Plans start at $15/month for up to 10,000 emails.

Price: Free for up to 100 emails/month, $15/month for up to 10,000 emails, $56/month for 50,000 emails, $115 for 125,000 emails, $255 for 300,000, $455 for 700,000, and $775 for 1.5 million emails. Custom plans are also available.

Best for: Small businesses and freelancers or those looking to get started with email sending

SparkPost (MessageBird)

SparkPost recently changed its name to MessageBird. For the sake of this article, we'll call them SparkPost. The company offers both SMTP and HTTP sending and is trusted by companies like Twitter, Airbnb, and Booking.com.

Libraries are available for PHP, Node, Go, and Python. The API is configured for top inbox placement with providers like Gmail. They offer a set of tools for monitoring sender reputation and resolving issues like hitting spam traps and blocklists.

The API is GDPR compliant and offers security through 2FA, intrusion detection, and email encryption. It is SOC 2 certified. You can authenticate via DMARC, SPF, and DKIM. The documentation is excellent and offers several quick-start guides and pre-built integrations. They also offer a collection that you can run in Postman.

You can start for free, and the free plan offers up to 50,000 emails per month. From there, plans start at $20/month.

Price: Free for up to 50,000 emails/month. $20/month for the starter plan up to 100,000 emails or $30 for additional features. $75/month for up to 250,000, $170/month for up to 500,000, $525 for up to 1 million, and custom plans available after that.

Best for: people just starting out all the way through enterprise companies


One of the most recognized names in email and SMS communication, Twilio's email API actually relies on SendGrid under the hood. As such, it offers essentially the same features at the same price as the SendGrid API.

Through the Twilio SendGrid API, you can directly deliver emails to Google, Yahoo, AOL, and Apple. It would make sense to choose this option if you are already using Twilio to handle other aspects of communication in your app (like SMS, for example.)

You can get started for free, then plans to start at $19.95/month.

Price: Free for life to send 100 emails/day, $19.95/month for 50,000 emails $89.95/month for 1.5 million+ emails, custom plans also available.

Best for: Businesses already using Twilio for other communication integrations

Side By Side Comparison





Free for life?

Price up to 10,000

Price up to 100,000












$35/month (50,000)







$19.95 (50,000)


Amazon SES



X up to 62,000 emails when sent via EC2 or EB

$0.10 per 1000

$0.10 per 1000






$115/month (125,000)






$20/month basic, $30 pro







$19.95 (50,000)


How to Choose the Best Email API for Your Business

As there are so many email APIs out there, you should evaluate your needs before choosing one. We recommend keeping the following factors in mind when choosing an email API service for your business email needs.

Consider Your Specific Needs

Do you need an API to handle validation? What about bulk sending? Are you concerned with deliverability or security? Is it important to be able to tell clients that you are using a recognizable and trusted brand?

Review API Documentation and Support

Support is critical, and not always readily available. Figure out what type of support you will need (are community forums enough or will you require personalized assistance via chat, email, or phone?)

Test the API

All of the options listed here offer a free plan or trial so you can test the API before committing.

Evaluate Costs and Pricing Plans

This should be the last thing you evaluate. It's better to figure out the features and support you need and then decide what you are willing to forego in order to come in under budget, rather than limiting yourself to a certain price from the get go.


What is an email API?

API stands for Application Programming Interface. It is a set of methods that allows two applications to interface with each other. An email API is a hosted email solution that allows developers to offload the work of email sending, receiving, tracking, and validation to a third-party service.

How does an email API work?

A typical email API exposes a REST endpoint that accepts network requests from an application with data to be processed. There are many different functions that an email API could perform.

Some email APIs handle sending and receiving, others handle validation, some might allow you to build your own email templates, while others send transactional emails or marketing campaigns.

What are the benefits of using an email API?

Using an email API means you don't have to code your own solution for common or difficult tasks. Since an email API is dedicated to handling email, they are very good at it and will likely do it better and faster than anything you could code yourself. Additionally, they provide authentication and security.

What are some email API implementation best practices?

Always handle errors correctly and surface user-friendly errors wherever necessary. Maintain your own logs to make debugging easier. Keep your API keys and secrets well protected. Monitor your connection to the API regularly to prevent downtime and other issues.


An email API is an excellent solution for businesses looking to offload the complexity of sending and receiving messages or validating email addresses. Allowing a third-party API (particularly one known to be reputable and trustworthy) to handle your SMTP communications will simplify your codebase, reduce bugs and maintenance, and improve email deliverability.

Ready to get started with an email API? Try out the AbstractAPI Free Email Validation and Verification API to validate email addresses from your mailing list.

4.7/5 stars (17 votes)

Boost your email deliverability and ensure a clean email list by trying out AbstractAPI's email validation API today.

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