Email communication plays a vital role in modern applications, enabling businesses to engage with users, deliver notifications, and facilitate seamless interactions. However, building robust email functionality from scratch can be a complex and time-consuming process. That’s where Email APIs come in, empowering developers to integrate email capabilities into their applications with ease.

What are Email APIs?

Email APIs are sets of protocols and tools that enable developers to integrate email functionality into their applications or software systems. These APIs serve as a bridge between the application and the email servers or services, allowing for seamless communication and interaction with email-related tasks.

Email APIs provide a standardized and structured way for developers to send, receive, manage, and automate email messages within their applications. They offer a wide range of functionalities and capabilities, including:

  1. Sending Emails: Email APIs allow developers to send automated emails programmatically. This includes sending transactional messages, notifications, marketing campaigns, and personalized emails to individual recipients or targeted lists.

  2. Receiving Emails: Email APIs enable the retrieval and processing of incoming emails within the application. Developers can receive and parse incoming emails, manage mailboxes, and handle email attachments.

  3. Managing Email Addresses: Email APIs provide functionalities to manage email addresses, such as adding or removing recipients from mailing lists, updating contact information, and handling unsubscribe requests.

  4. Templating and Personalization: Email APIs often include features to create and manage email templates, allowing developers to customize the content, design, and structure of emails. This enables personalization based on recipient data, such as names, locations, or preferences.

  5. Analytics and Tracking: Email APIs offer tracking capabilities to measure the performance and effectiveness of email campaigns. Developers can access metrics like open rates, click-through rates (CTR), bounce rates, and conversion rates to evaluate the impact of their email communications.

Types of Email APIs

When it comes to Email APIs, there are various types available to cater to different email-related needs. Let’s explore three common types: transactional, commercial, and mailbox provider APIs.

  1. Transactional Email APIs: Transactional Email APIs are specifically designed to handle transactional email messages, which are typically triggered by specific user actions or events. These APIs provide developers with the ability to send automated, personalized, and one-to-one emails to individual recipients. Transactional emails include notifications, account updates, password resets, order confirmations, and other similar communications. The focus of transactional Email APIs is to ensure the reliable and timely delivery of these critical emails. They often provide features like template management, email personalization, delivery tracking, bounce handling, and click/open rate reporting. Popular transactional Email API providers include SendGrid, Mailgun, and Sparkpost.

  2. Commercial/marketing Email APIs: Commercial/marketing Email APIs are designed for businesses that engage in email marketing and promotional campaigns. These APIs offer features to manage and send marketing emails to numerous recipients, typically in bulk. Commercial Email APIs provide functionalities for creating visually appealing email templates, managing contact lists, segmenting audiences based on demographics or preferences, scheduling email campaigns, and tracking campaign performance metrics like open rates, click-through rates (CTR), and conversions. They often include features for A/B testing, marketing automation, and advanced analytics. Popular commercial Email API providers include Mailchimp, Sendinblue, and Campaign Monitor.

  3. Mailbox Provider APIs (Gmail, Office 365, etc.): Mailbox Provider APIs, also known as Inbox APIs, allow developers to interact directly with specific mailbox providers such as Gmail, Office 365, or These APIs provide programmatic access to user mailboxes, enabling developers to read, send, and manage emails within those mail systems. They typically offer functionalities for retrieving email content, accessing folders and labels, managing drafts, sending new emails, and performing actions on behalf of users. Mailbox Provider APIs are useful for applications that require integration with specific mailbox providers to provide seamless email management and synchronization. Examples include applications that offer unified inbox experiences, email clients, or productivity tools. Some providers offer dedicated APIs for their platforms, such as the Gmail API and Microsoft Graph API.

Each type of Email API serves distinct purposes, catering to different aspects of email communication. Developers can choose the appropriate type based on their specific requirements, whether it’s sending transactional messages, running marketing campaigns, or integrating with specific mailbox providers to enhance email management within their applications.

Email deliverability

Transactional and Commercial Email API providers like SendGrid, Mailgun, Mailchimp send billions of emails on behalf of their clients daily using a shared IP address. This is what could negatively impact your sending reputation if you send emails using the same IP address as bad actors exhibiting spammy behaviors. Once an email service provider categorized an email as unwanted or unsolicited, they’ll aim to block future messages with similar characteristics.

Additionally, these vendors will send messages without differentiating the IP address between transactional and sales and marketing emails. The latter kinds of emails often yield higher bounce and unsubscribe rates, causing overall deliverability issues for every party using the mass email service.

You are in much better control of the email deliverability when using mailbox provider APIs, by allowing users to send messages directly from their email accounts versus a shared domain or IP address.

Conversational context

While some transactional and commercial Email APIs can be configured to receive emails from customers or other third parties, they may not provide the same level of conversational context and interactivity as the Inbox APIs. Transactional APIs are better suited for scenarios where customized conversations or ongoing discussions are not required, such as sending notifications or order confirmations.

The Inbox APIs are contextual as they are designed to facilitate personalized and interactive conversations via email. These APIs allow users to send messages directly from their own email addresses, customize each message with HTML and images. This enables a more natural and conversational communication flow between the sender and the recipient.

Relationship Management Intelligence

Through Inbox APIs, developers can gain valuable relationship management intelligence that helps them understand and engage with their customers more effectively.

Salesforce’s Einstein Activity Capture is an excellent example of how Email APIs can be utilized to enhance relationship management intelligence. It leverages Email APIs to capture and analyze email interactions, providing valuable insights to businesses for building stronger customer relationships.

Universal Email APIs

It is clear to us at Aurinko that developers should consider using mailbox provider APIs (Inbox APIs) when building differentiating communication features into their apps (such as deliverability, personalization, and conversation threading). However, you may ask about the multitude of providers.

That is where universal email APIs shine. A universal Email API serves as a bridge between developers and the diverse landscape of mailbox provider APIs. It acts as a layer of abstraction, simplifying the integration process and providing a unified interface for developers to interact with various email services.

With universal email APIs, developers no longer need to navigate the complexities of each individual mailbox provider’s API. They can leverage the standardized methods and data structures provided by the universal API to send, receive, and manage emails across multiple providers seamlessly.

One of the key benefits of a universal email API is its versatility. It supports integration with a wide range of mailbox providers, including popular services like Gmail, Office 365, MS Exchange and many others. This broad coverage allows developers to cater to a diverse user base without having to develop and maintain separate integrations for each provider.

By abstracting away the differences between mailbox provider APIs, a universal email API streamlines the development process and significantly reduces the time and effort required to build email-related features. Developers can focus on crafting engaging user experiences, leveraging the universal API’s capabilities to implement functionalities such as email notifications, threaded conversations, attachments handling, and more.

From a user standpoint, a universal Email API ensures a consistent experience across different mailbox providers. Users can seamlessly connect their email accounts from various services to the application powered by the universal API, enjoying a unified interface to access, compose, and manage their emails. This fosters user satisfaction and loyalty by providing a seamless and familiar experience, regardless of the specific mailbox service they use.


There are several remarkable Email APIs available that can enhance email communications and marketing efforts for businesses and organizations.

But when it comes to building communication features and enabling your app for relationship management intelligence, a universal Email API like Aurinko and especially its pre-built Email Sync should be at the top of your list. With its comprehensive features and seamless integration capabilities, Aurinko empowers product teams to incorporate robust email functionality into their business applications with ease.

By leveraging Aurinko’s unified API, developers can streamline email processes, improve deliverability, personalize messages, and improve their users’ experience. Take your app’s email capabilities to the next level and unlock the full potential of your communication features.

Choose Aurinko Email API and drive greater engagement and success for your app.