
The InboxSDK is a high level Javascript library used to easily build browser extensions that interact with both Gmail and Inbox by Google. It provides all of the necessary APIs to create full-fledged applications directly inside Gmail and Inbox. Because the SDK is fully maintained and evergreen, you’ll never be forced to maintain your app.
Compare InboxSDK to these popular alternatives based on real-world usage and developer feedback.

An easy to use email app that saves you time and keeps your messages safe. Get your messages instantly via push notifications, read and respond online & offline, and find any message quickly.

Twilio SendGrid's cloud-based email infrastructure relieves businesses of the cost and complexity of maintaining custom email systems. Twilio SendGrid provides reliable delivery, scalability & real-time analytics along with flexible API's.

Amazon SES eliminates the complexity and expense of building an in-house email solution or licensing, installing, and operating a third-party email service. The service integrates with other AWS services, making it easy to send emails from applications being hosted on services such as Amazon EC2.
Mailgun is a set of powerful APIs that allow you to send, receive, track and store email effortlessly.

Mandrill is a new way for apps to send transactional email. It runs on the delivery infrastructure that powers MailChimp.

Postmark removes the headaches of delivering and parsing email for webapps with minimal setup time and zero maintenance.

It is an application that is used mainly to send and receive emails. It can also be used to manage various types of personal data including calendar appointments and similar entries, tasks, contacts, and notes.

It is a single module with zero dependencies – code is easily auditable. The email delivery is Secure using TLS/STARTTLS. You can use HTML content, as well as plain text alternative.

Mailjet is a real-time Cloud Emailing platform: scalable, agile and flexible. Our unique algorithm boosts your deliverability and our platform provides in-depth insight so you can optimize more than ever.

SparkPost is the world’s #1 email delivery provider. We empower companies with actionable, real-time data to send relevant email to their customers which increases engagement and both top and bottom line revenue.

It is a free and open-source mail transfer agent that routes and delivers electronic mail. It is Wietse Venema's mail server that started life at IBM research as an alternative to the widely-used Sendmail program. Now at Google, Wietse continues to support it.

We offer one platform that covers all email-related needs in one place: testing, sending, and in-depth tracking to control how email infrastructure works and performs.

Litmus is a testing service for web and marketing professionals. It allows people to cross-browser test their websites, and test their email newsletters across a range of email clients and spam filters.

It is the world's largest secure email service, developed by CERN and MIT scientists. We are open source and protected by Swiss privacy law

Send email from your app with a simple API call, Sendwithus manages the rest. Templates, testing, data management, segments, and analytics are all accessible through a friendly dashboard.

It is a modern email sending platform focused on providing the best developer experience. Build, test, and deliver transactional emails at scale.

As soon as a mailbox is connected, we create a metadata index of its content starting from the most recent emails which become available from the API within seconds. Context.IO takes care of synching email data for your app so you don't have to build, scale and maintain this infrastructure yourself. Focus on what's unique to your business, we'll manage the technical details of integrating with arcane email server protocols.

A full-featured email creation and transfer class for PHP. It is a class library for PHP that provides a collection of functions to build and send email messages. PHPMailer supports several ways of sending email: mail() , Sendmail, qmail & direct to SMTP servers.

Mixmax’s mission is to do the impossible with email. We believe everything you do today on the web should be possible in any email. This includes scheduling meetings, completing surveys, making purchases, playing games, and even interacting

It is an open source IMAP and POP3 email server for Linux/UNIX-like systems, written with security primarily in mind. It is an excellent choice for both small and large installations. It's fast, simple to set up, requires no special administration and it uses very little memory.

Email on Acid is the most affordable, self-serve email testing platform in the world. We can help you maximize the success of your email marketing efforts by diagnosing and improving your renderability, deliverability, click-throughs and conversions.

It is an email testing tool for developers. You can configure your application to use MailHog for SMTP delivery. You can view messages in the web UI, or retrieve them with the JSON API.

It is an open source server and secured & fast customer software for messaging and collaboration. The software consists of both client and server components, and a desktop client. It also provides native two-way sync to many mobile devices.

It is a free feature-rich email service with unlimited mailbox size. It has two-factor authentication and login history to prevent hacking. It scans all incoming mail for both spam, phishing, and malware.

Work smarter with business-class email and calendaring. It helps you collaborate on your critical documents and gives you a focused inbox that prioritizes important messages and adapts to your work style.

It is a cross-platform mail client library built on top of MimeKit. The main goal of this project is to provide the .NET world with robust, fully featured and RFC-compliant SMTP, POP3, and IMAP client implementations.

Email Blueprints is a collection of HTML email templates that can serve as a solid foundation and starting point for the design of emails. They include template language elements that make them customizable when imported into a MailChimp account, as well as merge tags that will generate dynamic content when sent through MailChimp. Not a MailChimp user? You can sign up free or simply strip out merge tags and use these templates to send through any system.

It adds scheduled sending and the easiest, most integrated email reminders to Gmail, helping you reach Inbox Zero.

It allows sending email directly from Javascript, with no backend development. The developers create one or more email templates (dynamic content supported) and then trigger an email using our Javascript SDK, specifying the template, and the dynamic parameters for rendering the email.

A new kind of transactional email service designed for developers to work faster and smarter with a powerful infrastructure to scale quickly.

It is a premium email delivery and email relay solution that enables you to send and track high volume emails effortlessly. Integrate and start sending in minutes.

250ok is an email deliverability tools company that produces a Software‐as‐a‐Service (“SaaS”) platform to monitor and measure the deliverability of email networks. These networks consist of companies sending various forms of messages including marketing, transactional, share, and others from various platforms.

Kickbox ensures you only send email to real users and helps you separate the low-quality addresses from high-value contacts. Protect your reputation, increase open rates, and save money with Kickbox.

Email deserves a dust off. A renovation. Modernized for the way we email today. With HEY, we’ve done just that. It’s a redo, a rethink, a simplified, potent reintroduction of email. A fresh start, the way it should be.

It runs a super simple SMTP server which catches any message sent to it to display in a web interface. It catches all mail and stores it for display. It shows HTML, Plain Text and Source version of messages, as applicable.

For the best HTML e-mail delivery results, CSS should be inline. This is a huge pain and a simple newsletter becomes un-managable very quickly. This script is the solution.

Postal is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready for you to run on your own servers. Postal was developed by aTech Media to serve its own mail processing requirements and we have since decided that it should be released as an open source project for the community.

Using only real-time verification, NeverBounce offers the highest accuracy. No historical data used. Under a penny per email. We’ll beat any major competitor’s pricing.

It is a free, open source mail server solution for your favourite Linux/BSD. You can deploy an open source, fully fledged, full-featured mail server in several minutes, for free.

A Node.js package that generates clean, responsive HTML e-mails for sending transactional mail.

It allows you to upload and validate lists of email addresses quickly and in a secure way. All you have to do is upload an email list to it's web interface. It also offers API.
Transactional HTML emails often get neglected. Styling HTML email is painful. Tables, inline CSS, unsupported CSS, desktop clients, web clients, mobile clients, various devices, various providers. We’ve tried to remove some of the pain for you and open-sourced a collection of common templates for transactional email.

Mailinator is a disposable email service that allows QA departments to test with 1000's of inboxes.

Ink is a responsive email framework, used to make HTML emails look great on any client or device. It includes a 12-column grid, as well as some simple UI elements for rapid prototyping.

Automate email and SMS tests, like account verification and password resets, using any language or testing framework using the Mailosaur API. Stop email being delivered to customers using fake SMTP servers.

It is an email delivery service for your transactional and marketing emails. It replaces your email infrastructure so you don’t have to build, scale, and maintain these systems in-house. With an easy SMTP service you can start quickly, while our robust API gives you full control over email processing and reporting. Your transactional emails are delivered instantly and your marketing campaigns can be scaled to millions.

Stay out of trouble. Validate your email addresses before you send. BriteVerify can reduce your bounce rate by 98% and help your messages get delivered. So stop bouncing and start converting your prospects into customers with BriteVerify True Email Verification™.

It is collection of high-quality, unstyled components for creating beautiful emails using React and TypeScript. It reduces the pain of coding responsive emails with dark mode support. It also takes care of inconsistencies between Gmail, Outlook, and other email clients for you.

It helps build lasting business relationships, right from your inbox. A sales engagement platform designed for sales professionals and account managers.

mailparser.io is a web-based email processing software which allows you to pull any kind of data from incoming e-mails based on custom parsing rules. The parsed data can be sent to any API with webhooks.