What is an Email API?

An email API, or application programming interface is a tool that enables developers to easily access data and functions offered by email service providers (ESPs) — such as Gmail, Microsoft Outlook, Yahoo! Mail, and others. By building integrations with email APIs, developers can quickly build applications allowing end-users to generate and send messages, manipulate templates, move or edit folders, build drafts, and perform additional email functions without switching between multiple platforms.

Why it’s mission-critical to build bi-directional email in your CRM with an email API… now

Email API providers take care of protocol matters such as message assembly, message sending, and reporting that would otherwise need to be specified by a business’s application software development team. On top of that, email APIs enable powerful data analytics — which you otherwise wouldn’t get by integrating with the ESP directly.

Why do you need an email API? 

Email is the most popular communication channel globally, with users sending more than 306 billion emails daily. And many of these communications occur between businesses and their customers, prospects, partners, and employees. 

For your users, drafting emails from scratch can take valuable hours and resources, especially when sending similar messages repeatedly. It’s easy to fall into a pattern and become complacent, leading to errors and inconsistencies in content. 

For your developers, building custom integrations with each email service provider wastes resources that could be better spent advancing your roadmap. Writing software to automate emails from scratch is possible but requires constant maintenance and often results in a substandard user experience. Doing so at scale to thousands of people is nearly impossible without the help of a dedicated development team.

Email APIs provide businesses an efficient, customizable, and secure way to send and receive emails within their platforms and applications.

Email API Example

Email APIs allow developers to integrate email functionalities with minimal coding. For example, if you wanted get the last 5 messages from a user’s inbox, you would use this code:







app.get("/nylas/recent-emails", async (req, res) => {
 try {
   const identifier = process.env.USER_GRANT_ID;
   const messages = await nylas.messages.list({
     queryParams: {
       limit: 5,

 } catch (error) {
   console.error("Error fetching emails:", error);
require 'nylas'

nylas = Nylas::Client.new(api_key: 'API_KEY')
query_params = { limit: 5 }
messages, _ = nylas.messages.list(identifier: '<GRANT_ID>', query_params: query_params)

messages.each {|message|
 puts "[#{Time.at(message[:date]).strftime("%d/%m/%Y at %H:%M:%S")}] \
from dotenv import load_dotenv

import os
import sys
from nylas import Client

nylas = Client(

grant_id = os.environ.get("NYLAS_GRANT_ID")

messages = nylas.messages.list(
   "limit": 5

import com.nylas.NylasClient;
import com.nylas.models.*;
import java.text.SimpleDateFormat;

public class ReadInbox {
 public static void main(String[] args) throws NylasSdkTimeoutError, NylasApiError {
   NylasClient nylas = new NylasClient.Builder("<NYLAS_API_KEY>").build();
   ListMessagesQueryParams queryParams = new ListMessagesQueryParams.Builder().limit(5).build();
   ListResponse<Message> message = nylas.messages().list("<GRANT_ID>", queryParams);

   for(Message email : message.getData()) {
     String date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").
         format(new java.util.Date((email.getDate() * 1000L)));

     System.out.println("[" + date + "] | " + email.getSubject());
curl --request GET \
  --url "https://api.us.nylas.com/v3/grants/NYLAS_GRANT_ID/messages?limit=5" \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer <NYLAS_API_KEY_OR_ACCESS_TOKEN>' \
  --header 'Content-Type: application/json'   
  "request_id": "d0c951b9-61db-4daa-ab19-cd44afeeabac",
  "data": [
          "starred": false,
          "unread": true,
          "folders": [
          "grant_id": "1",
          "date": 1706811644,
          "attachments": [
                  "id": "1",
                  "grant_id": "1",
                  "filename": "invite.ics",
                  "size": 2504,
                  "content_type": "text/calendar; charset=\"UTF-8\"; method=REQUEST"
                  "id": "2",
                  "grant_id": "1",
                  "filename": "invite.ics",
                  "size": 2504,
                  "content_type": "application/ics; name=\"invite.ics\"",
                  "is_inline": false,
                  "content_disposition": "attachment; filename=\"invite.ics\""
          "from": [
                  "name": "Nylas DevRel",
                  "email": "nylasdev@nylas.com"
          "id": "1",
          "object": "message",
          "snippet": "Send Email with Nylas APIs",
          "subject": "Learn how to Send Email with Nylas APIs",
          "thread_id": "1",
          "to": [
                  "name": "Nyla",
                  "email": "nyla@nylas.com"
          "created_at": 1706811644,
          "body": "Learn how to send emails using the Nylas APIs!"
  "next_cursor": "123"

Alternate methods to email APIs

Before email APIs became widely available, businesses would typically use one of the following methods to send and receive emails:

  • Simple Mail Transfer Protocol (SMTP) — This was defined as the standard internet protocol for email communications back in 1982 and is still the de facto protocol when sending or receiving email from outside one’s own systems. While SMTP is still widely used, it is not ideal for application-to-application communication as it requires significant setup and maintenance. SMTP offers the finest granularity for control but demands attention for every little interaction, which adds up to considerable network traffic overhead and more potential points of failure that break the chain.
  • Post Office Protocol Version 3 (POP3) — This one-way protocol retrieves emails from a remote server and sends them to a remote client. POP3. If the email is deleted from the server, it will also be deleted from the client’s device, making this method less than ideal for applications that must store and analyze large amounts of email data.
  • Internet Message Access Protocol (IMAP) — IMAP was initially designed as a better alternative to POP3. Similar to POP3, IMAP is used to retrieve emails from a server; however, it allows the client to keep a copy of the email on the server so messages can be accessed from multiple devices. While IMAP is more scalable than POP3, it still requires a lot of setup and maintenance.

Overall, these older methods of sending and receiving emails are less scalable and sustainable than email APIs. Email APIs provide a more efficient and reliable way to send and receive emails, with built-in security, spam filtering, and analytics.

Build for free with Nylas API

Focus on your business strategy, NOT on infrastructure. Investing in pre-built productivity tools frees up resources so your team can focus on building unique features your customers love.

Build for free

Types of email APIs

Email APIs fall broadly into two categories: transactional and contextual email APIs. Transactional and contextual email APIs serve different purposes, so it’s not necessarily a matter of one being better. Many business use cases require multiple email APIs to deliver a convenient, unified customer experience (see here for more information on how product teams use combined transactional, contextual, and marketing email APIs). 

Transactional email APIs

Transactional email APIs send bulk or routine emails like notifications, password reset emails, and mass marketing campaigns through third-party email providers. These APIs can be specifically tailored to avoid mass marketing campaign flags. Mailgun, MailChimp, and SendGrid are examples of well-developed transactional email API providers. Transactional APIs are crucial because they allow businesses to automate essential communication with customers, improve email deliverability, and provide valuable insight into email engagement.

Contextual email APIs

Contextual email APIs embed robust email connectivity directly into software applications. Productivity tools, customer relationship management (CRM) platforms, applicant tracking systems, and car consoles use email APIs. Contextual emails allow you to send, receive, and collect analytics and handle general create, read, update, and delete (CRUD) functions for each ESP. The Nylas Email API is an example of a contextual email API, acting as a layer of 

abstraction on top of all email providers. 

Learn more about Transactional email APIs vs Contextual email APIs here.

Email API features 

Email APIs are not all created equal. Some email APIs offer more advanced features, better performance, and greater reliability. Businesses and developers should carefully consider the features they need from an email API when selecting a solution and choose one that best fits their needs and requirements.

Here’s a list of features that should factor into your decision-making when tackling email integration:

  • Bi-directional email sync — This feature ensures that the latest conversation history is available in real-time — both in your application and your users’ email client.
  • Auto-complete contacts — With a contacts API, users can synchronize contacts between an email server and an application, making it easy to access and use email contacts for various purposes, such as managing email marketing campaigns or tracking applicant communications. 
  • Send emails — Once you integrate with an email API, users can send emails from your application without using a separate email client. As part of the ability to send emails from an application, users can benefit from other productivity-enhancing features like mail merge, which streamlines the process of creating multiple pieces of personalized content from an existing template.
  • Receive emails While most email APIs enable users to send emails from their platforms, not all email APIs allow applications to receive emails. APIs designed for sending and receiving emails will typically provide a more comprehensive set of features for managing email communications. For example, these APIs may include advanced email filtering and parsing capabilities, support for multiple email protocols, and the ability to process email attachments.
  • Email tracking — With detailed insights into email performance, businesses can see which emails are performing well and which are not. Businesses can track email metrics, such as open, click-through, and bounce rates. This data can be used to improve email campaigns and optimize email content.
  • Email inbox parsing — This feature allows businesses to extract unstructured data from incoming emails, such as the sender, recipient, subject, and body. Data can be used to trigger specific actions or workflows within the application, such as processing orders or responding to customer inquiries.

These API features can help businesses improve email communications, automate various tasks, and gain valuable insights into email performance.

Benefits of using an email API 

Businesses and developers may use an email API to add email capabilities to their website or application, as building this functionality from scratch can be challenging. This process is time-consuming for a large development team, but this effort is multiplied for small teams or solo developers. 

Email APIs offer a range of benefits for teams of any size, such as: 

  • Fast implementation — Email APIs abstract away most of the traditional burden of building and maintaining integrations between your app and the service providers your customers’ service providers, leading to an accelerated time-to-market. 
  • Cost savings at scale — According to Gartner, only 11% of organizations maintain cost savings for three consecutive years. Email APIs eliminate the need to develop and maintain custom integrations for each application or system you use, saving cumulative time and money in the long run. 
  • Ease-of-use — Email APIs should provide your developers with clear documentation, sample code, and support for popular programming languages and frameworks. They will also have a user-friendly interface that allows developers to manage and customize email functionality without requiring extensive technical knowledge.
  • Deep personalization — Email data is unstructured, making extracting and integrating value into a company’s data stack challenging. Email or inbox parsers — features of a robust email API — can help extract, structure, and categorize unstructured email data, which can then be used for hyper-personalization and to improve the end-to-end customer experience.
  • Enterprise-grade security — Email APIs handle sensitive data, such as user credentials and email content, so they are likely equipped with comprehensive security measures. This includes encryption, authentication, authorization protocols, and compliance with industry standards and regulations like GDPR and HIPAA.
  • Improved deliverability — Email APIs often support email authentication protocols such as SPF, DKIM, and DMARC. These protocols help verify that the email message is legitimate and not sent from a spammer or a fraudulent source, improving the chances of the email being delivered to the recipient’s inbox rather than being marked as spam. Similarly, integrating directly with an email service provider yields higher deliverability rates than using a transactional API, as recipients are far less likely to mark email from a personal address as SPAM. 

One of the top three reasons our customers churn was email deliverability. Nylas solved a top three problem for us overnight. We went from close to 0% to nearly 100% deliverability.

Justin Belobaba

CEO at Now.Site

Building vs. buying an email API solution 

When tasked with adding email capabilities to your platform or application, you and your developers must decide whether to build the integration in-house or adopt an Email API solution. Both options have different benefits and drawbacks, and the choice will depend on your business’s resources, needs, and goals.

Building an email integration that spans all providers can take more than a year, quickly accrue costs, expend developer resources, and disrupt your product roadmap. Furthermore, the risk involved when teams attempt their own email integration is a significant technical and legal concern. To build email integrations, you must understand complex protocols (such as SMTP, POP3, and IMAP) and have the expertise to navigate security measures. As email integrations involve sensitive user data, you also must know and comply with data privacy laws like General Data Protection Regulation (GDPR) and the California Consumer Privacy Act (CCPA)

Consider these points to help you decide whether to develop or purchase your next integration or platform capability: 

  • Budget — Building your own solution is a hefty investment that requires the right personnel with subject-matter expertise and a deep understanding of security and policy requirements. Even with the best development and tech teams, constantly developing new features and maintaining old ones can be time-consuming and costly. 
  • Software scope — The more complex your project is, the more difficult it will become to build and maintain. Making software with unique features will take more custom work and effort to run effectively. 
  • Scalability — The complexity of building a single integration is already challenging. When you consider the accompanying costs and time of maintaining this infrastructure, it becomes an even more significant undertaking. Each time you need to add a new integration, you’ll have to build it out. 
  • Security — When building a software solution, the control over the system can be tailored. But, it requires more resources to implement and continuously monitor an air-tight system. You may even have to invest in an external, expensive security solution.
  • Control — Building your own solution might feel like you have more control over your platform. But in reality, it’s limited to what your developers can do in the time they have left.

These caveats often prompt companies to integrate with an email API. Doing so enables developers to easily add full email functionality, ship products quickly, and go to market faster. For developers, an email API abstracts away the messy details of sending in-app communications using traditional protocols and allows them to dedicate their efforts to more meaningful product differentiators.

Steps to implement an email API service

Businesses and their developers can use email APIs to send and manage messages programmatically. 

Here are the steps to getting started:

  1. Sign up for an email API The first step is to select an email API provider and sign up. Once signed up, businesses and development teams can access the API’s documentation or sample code and follow the steps to integrate it into their application or website.
  2. Set up email templates — The next step is to create email templates that can be used to send messages to your desired audience. These templates can include dynamic content, such as customer names, purchase details, or promotional offers.
  3. Configure email settings — Businesses can configure email settings such as sender name and address, reply-to address, and subject lines. They can also set up email authentication, such as SPF, DKIM, and DMARC, to ensure their messages are delivered and not marked as spam.
  4. Monitor and analyze performance — Once integrated, businesses can monitor and analyze the performance of their email campaigns. They can track open, click-through, and conversion rates to optimize email marketing efforts.

Overall, businesses and their developers can use an email API to programmatically send personalized and targeted email messages, improve the reliability and scalability of their email service, and monitor and analyze the performance of their campaigns.

Ship faster with the Nylas Email API 

Email integration has always been a profoundly technical challenge for any developer who wants to build comprehensively and move fast. But with the advent of cloud server architecture and API-driven email service platforms, companies can add complex, highly performant email functionality into their applications with little or no knowledge of email administration or telecommunications protocols. 

Partnering with an email API provider offers a streamlined workflow for quickly integrating functionality and grants features such as service reliability guarantees and analytics reports. Get started today and build for free with Nylas email API.

Frequently Asked Questions

What is an email API?

Email API is an application programming interface that enables developers to interact with email service providers like Gmail, Microsoft Outlook, and Yahoo! Mail. It simplifies the process of building applications that allow end-users to send emails, manage templates, organize folders, create drafts, and execute other email-related tasks without having to switch between different platforms.

How do you create an email API?

Creating an email API is a complex and challenging task that involves defining endpoints, methods, parameters, and security protocols to enable developers to interact with an email system. It requires a deep understanding of email technology and protocols and expertise in API development, programming languages, and frameworks. 

What is an example of an email API?

There are several email APIs available that allow developers to integrate email functionality into their applications or platforms. One example is Nylas — the fastest and easiest way to connect to your users’ inboxes, powering engaging, embedded email capabilities with 99.6% deliverability and enterprise-grade security. In addition to email, the Nylas platform powers calendar and contacts integrations.

Other popular email APIs include SMPT.com, SendGrid, Mailgun, Twilio SendGrid, Amazon SES, and Postmark. Businesses and their developers should choose an email API that best suits their needs based on cost, features, and ease of integration.

Nyla waiving Nylas flag

Ready to get started?

Unlock your API key and sync up to 5 accounts.

Additional Resources

10 Best Email APIs in 2023
10+ best email APIs in 2023 for developers [free & paid]
hero banner image for blog post
How to improve email deliverability?
How to create a mail merge template with Ruby