What Are Email APIs?

August 24, 2023
Written by
SendGrid Team
Opinions expressed by Twilio contributors are their own
Reviewed by
Ayanna Julien
Opinions expressed by Twilio contributors are their own

What Are Email APIs?

An application programming interface (API) allows two software applications to interact with one another through well-defined protocols and methods. Within the context of email, an email API allows applications to interact with an email service. This communication interface enables programmatic processes such as sending, receiving, and tracking emails.

The emergence of email APIs has significantly impacted how businesses digitally communicate with customers. Such programmatic emailing through email APIs reshapes how businesses handle email interactions by bringing automation and customizability.

In this guide, we’ll unpack email APIs, highlighting the functionality and benefits. Then, we’ll dive into practical steps—how to use email APIs, whether to build or buy, and what to look for in an email API.

Let’s start with some foundational concepts.

How does an email API work?

At its core, an email API acts as a liaison between an application and an email service provider (ESP). Rather than opening an email client, composing an email, specifying a recipient and a subject, and clicking Send, your software application can piece together the information needed for an outgoing email, then send a request with that information to an email API. The API accepts this request and communicates it to the email service, which subsequently sends the email.

As mentioned earlier, with an email API, you can programmatically handle sending, receiving, and tracking emails. 

Let’s illustrate with a scenario. Suppose you have an online store and want to send a confirmation email to a customer immediately after they make a purchase. Without an email API, you would need to wait for a notification from your application that you received a new order. Then, you would open an email client to draft and send an order confirmation email to your customer. This might be acceptable if you receive one order every few days, but it’s neither scalable nor reliable. Consider the following:
  • What if your store grows to receive dozens of orders daily?
  • What if you want to go on a vacation for a few days but still need to send confirmation emails?
  • What if you have more important things to do than wait for order notifications and send emails?
With an email API, your application can send an API request to the email service to send the order confirmation email immediately following a purchase. Of course, the request will include all the relevant details—such as the customer’s email address, the subject line (“Your order has been confirmed!”), and the body of the email (with order summary and shipping details). However, the email API performs all this programmatically, fully automated.

By leveraging an email API, your business can ensure smooth and timely communication with your customers without manual intervention from you or your employees.

Types of email APIs

Email APIs can be feature-rich, and your specific need or use case may dictate the type of email API you ought to use. In general, we can categorize email APIs into the following main types:
  • Send APIs facilitate email sends. You can use email send APIs to automate transactional emails, such as order confirmations or password reset requests. In addition, you can send APIs for commercial purposes, such as opt-in promotional emails or surveys.
  • Receive APIs handle incoming emails. You can use receive APIs to parse inbound emails and automate processes based on the content. For example, when your customer service agent and a customer communicate via email, a customer reply can automatically trigger a support ticket update.
  • Tracking APIs retrieve tracking and statistical data on outbound emails. Closely related to send APIs, some tracking API services may integrate functionality directly into the send API instead of offering a separate tracking API.
Also worth mentioning are webhooks. While not technically an API, these play a critical role in the API ecosystem. A webhook is an HTTP request sent by an email service (typically to a URL you choose) whenever certain events occur, such as opens, clicks, bounces, and delivery confirmations. Your software application might have an API endpoint that could function as a webhook target. This allows you to process incoming webhook requests for tracking and monitoring email performance.

What type of email API is right for you?

The right email API for you depends on your business requirements. Use the following scenarios to help point you in the right direction:
  • Are you primarily sending automated, transactional emails to customers? If so, a send API will be your best choice.
  • Does your application need to react to incoming emails by performing specific actions or updating database records? If so, a receive API will meet your needs.
  • Are you most interested in tracking information about emails you’ve sent? If so, a tracking API and webhooks might be the best choice.
Although your unique business scenario will guide your choice, fortunately, most providers that offer email APIs will give you access to sending, receiving, and tracking APIs. The providers will likely have webhook functionality too.

Email APIs versus SMTP

The Simple Mail Transfer Protocol (SMTP), which has been around since the 1980s, is a communication protocol used by mail servers for sending and receiving email. Many email clients use SMTP for sending email messages to a mail server.

ESPs still use SMTP with their servers, and many give users the ability to communicate directly with those servers via SMTP. However, for sending emails programmatically, an email API is a more modern and versatile approach.

Benefits of using an email API

Businesses that communicate with customers digitally need efficiency, scalability, and customizability. This is where email APIs can benefit operations significantly. Here are the advantages of integrating an email API within your existing applications:
  • Increased efficiency: An email API saves you valuable time and resources as you automate workflows. Whether sending individual, personalized transactional email messages or thousands of emails for a marketing campaign, an email API streamlines your process.
  • Greater flexibility: An email API gives you greater control over how to customize and personalize your emails, including tailoring the content, formatting, and sending options to your recipients. For example, consider giving customers the choice of their preferred time of day for receiving a daily digest email of recent announcements.
  • Enhanced deliverability: An email API often has built-in features to improve email deliverability, such as handling bounces and spam complaints. These measures help to protect your sender reputation so that your emails reach your customers' inboxes.
  • Scalability: An email API scales with your needs. As your user or customer base grows, you can have confidence that your email system can handle it.
Now that we've outlined the potential benefits of using an email API, the next step is understanding how to effectively use one.

How to use an email API

Getting started with using an email API requires three steps. Here, we’ll walk you through how to send your first email with the Twilio SendGrid Email API.

1. Sign up for a free SendGrid account.


2. Navigate to SettingsAPI Keys after logging in. Click on Create API Key. Then, create a new API key with Full Access and give it a name. Copy your new API key (it should begin with SG) and put it somewhere safe for later access.



3. Use curl to send a request to SendGrid’s Mail Send API endpoint. Requests to SendGrid’s Email APIs use Bearer Authorization with your API key. A sample request looks like this:


Voilà. You’ve sent your first email through an email API. For a more detailed walk-through, read one of our getting started guides.


Key considerations when using an email API

Using an email API offers several advantages. However, using an email API effectively and responsibly requires keeping the following key considerations in mind:
  • Security: Safeguard your email API keys since these provide you access to your email service. API keys should never be hardcoded into your application or committed to your code repository.
  • Rate limits: Be aware if your ESP imposes an API rate limit, which is the number of requests an API will accept within a certain time frame. If you exceed these limits, your provider could throttle or block further requests.
  • Error handling: Implement robust error handling in your code to maintain a smooth user experience even when things go wrong, such as network issues, malformed requests, or other issues that may lead to failed API calls.
  • API updates: Stay up to date with any updates and changes to the API. These changes may affect how your software application interacts with the API.

Should you build or buy an email API?

A typical question of organizations considering an API revolves around whether to use a prebuilt solution or build one. While building an API might seem appealing with the level of customization that it offers, this approach takes a considerable investment of time and engineering resources.

On the other hand, using a prebuilt API brings many advantages:
  • Frees up engineering resources: Your engineering team can concentrate on primary business tasks if you choose a prebuilt API.
  • Lower costs: You avoid considerable upfront costs and ongoing expenses for development and maintenance by not creating your own API.
  • Faster deployment: You can significantly reduce your application’s time to market with the quick integration of an existing email API.
  • Expert support: You gain access to experts who facilitate email when you purchase a prebuilt API. This means you can focus on your unique business areas while depending on the expertise of those who focus on email.
In light of these reasons, it's clear why many organizations choose to purchase a prebuilt email API. Next, let’s look at the features to keep in mind when considering third-party email API services.

Features to look for in an email API

Choosing the right email API is a strategic decision, and the one you choose ought to align closely with your specific business needs. When considering your options, look for:
  • Deliverability: This means the API ensures your emails successfully reach the recipients’ inboxes, rather than getting sent to spam or bouncing back. ESPs with strong sender verification and vetting practices typically have better rates of deliverability.
  • Reliability: This means minimal downtime and consistent performance. Your emails will be critical to your business, and you can’t afford to depend on regularly slow or unavailable service.
  • Scalability: This means an API’s ability to handle an increased load as your business grows. Your email volume should grow in proportion to your business, as should your email API must be able to grow as you do.
  • Support: This means providing assistance to troubleshoot and quickly resolve any issues. When your application depends on an email API, you must have confidence that the team behind that email API will be prompt and responsive to your inquiries and needs.
  • Security: This means prioritizing secure practices, such as encryption and secure API keys. Because your emails might transmit sensitive customer information, the email API you use must provide adequate security measures.

Get started with Twilio SendGrid's Email API

Switching from SMTP and direct email composition to a programmatic email API offers many benefits, including automation and scalability, that will far outweigh the effort you put into the transition. In addition, if you use Twilio SendGrid’s Email APIs, the process is straightforward.

After setting up your SendGrid account and obtaining an API key, choose whether to use SendGrid’s APIs directly (via HTTP requests) or leverage an SDK. SendGrid maintains official libraries for its mail-sending API for seven different languages:
  • C#
  • Go
  • Java
  • Node.js
  • PHP
  • Python
  • Ruby
When building an application with one of these languages, you’ll have a faster integration experience by using the language-specific libraries. However, if your development uses a language not listed above, you can always leverage an open-source library contributed by the SendGrid Community.

As we've explored in this guide, using an email API brings many benefits, including improved deliverability, security, and scalability. By opting to integrate a prebuilt solution like SendGrid, you reduce your development complexity while keeping your costs low. 

Ready to dive into the world of SendGrid Email APIs? Sign up for a free account.

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