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 APIs
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 APIs
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.
AbstractAPI
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
Mailgun
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.
You can get started with the Mailgun API for free. The free plan is a 1-month trial and allows you to send up to 5000 emails (to validate emails, you’ll have to upgrade.) Once you’ve signed up with an email address and password, you’ll land on a dashboard that shows you at a glance your sending stats—percentage that have been delivered, percentage failed, and percentage suppressed. There’s also a handy graph showing your analytics for the last 30 days, and a button to test your inbox placement, which allows you to see where your emails are most likely to land before you send them. Adding your own custom sending domains is quick and easy to manage.
SendGrid
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.
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. SendGrid is now managed by Twilio, so when you login via the SendGrid site, you will be redirected through a Twilio login. Honestly, it’s confusing: if you already have a Twilio account, you can log in with that, but then you are taken through an additional Sendgrid login that appears to want the same information, but shows an error if you use the same username/email as your Twilio account. After you’ve been dumped out onto the homepage, if you click “Start for Free” again, it seems to log you in fine, but eventually, you end up at the same error screen again.
Frankly, the whole process of simply logging in to this service was so painful that I eventually gave up. Perhaps it’s easier if you have never created a Twilio login before. But there are so many other email APIs to choose from, why bother wasting your time?
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. There are 3 ways to send email with SES - via the console, via the SMTP interface, or via the API. I found it easiest to use the API in conjunction with the SDK they provide. The SDK exposes handy methods like SendEmail, which can be fed strings that will be injected into a formatted email.
SES does not provide email validation - it is for sending and receiving emails programmatically. In order to validate emails, you’ll need to chain it with another service, like AbstractAPI.
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
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. Once you’ve signed up for a free account, you’ll land in the dashboard. The way Postmark is set up is a little confusing at first—they separate different types of emails into different “Message Streams.” Transactional streams are for time-sensitive emails triggered for one user at a time, broadcasts are for emails sent to many users at once, like marketing campaigns, and the inbound stream is for your application to receive emails.
In order to send an email, you “Create a Message Stream” and choose what type of stream it should be. Postmark attests that this helps message deliverability, but honestly, it’s unclear how this helps. They also provide HTML templates for formatting nice-looking emails.
Your account will be in “test mode” until you submit a request for approval, so you’ll only be able to send 100 emails. You can send unlimited emails to your own domain during this time.
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. Once you sign up, you’ll need to add your verified sending domain before you can start sending. Sparkpost guides you through it step by step and they make the process very easy. Once you’ve done that, you can download an API key. The UI is pretty bare bones and it took me a while before I realized that you can’t actually send emails from the web app—you can only send them programmatically. Compared to other services, Sparkpost is a little more involved to set up, but their documentation is very clear and makes it pretty straightforward.
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
Twilio
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. You can’t easily access SendGrid functionality from Twilio—if you log in to Twilio, there is nothing in the UI that indicates that you can even use the service to send emails. I recommend logging in via SendGrid—although that process, as explained above, is painful. Honestly, I think Twilio is probably better for phone numbers and messaging. If you’re already using Twilio for another service, adding on SendGrid functionality probably makes sense, but if you’re just looking for a robust, easy-to-use email API, check out one of the other options on this list.
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
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.
FAQs
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.
Conclusion
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.
