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What is EmailEngine?

EmailEngine is a self-hosted email gateway that allows you to access email accounts over REST API. It provides a unified interface to interact with IMAP and SMTP protocols, as well as native integrations with Gmail API and Microsoft Graph API.

One REST API covers every account type it supports:

  • IMAP - Standard email protocol
  • SMTP - Standard email sending protocol
  • Gmail API - Native Gmail integration
  • Microsoft Graph API - Native Microsoft 365/Outlook integration

What EmailEngine is NOT​

Understanding what EmailEngine does not do is as important as knowing what it does:

Not a Mail Server​

EmailEngine is not a mail server like Postfix, Sendmail, or Microsoft Exchange. You cannot create new email accounts with EmailEngine. It does not host mailboxes, manage email domains, or provide MX records for receiving mail directly.

Instead, EmailEngine connects to existing email accounts that you already have with providers like Gmail, Outlook, or any IMAP-compatible email service. Think of it as a bridge between your application and email providers, not as a replacement for those providers.

Not a Managed Service​

EmailEngine is self-hosted software, not a cloud service. There is no EmailEngine-hosted API endpoint you can call. You must deploy and run EmailEngine on your own infrastructure, whether that's:

  • A cloud server (AWS, DigitalOcean, Render, etc.)
  • An on-premise server
  • A Docker container
  • Your local development machine

This gives you complete control over your data and privacy, but also means you're responsible for hosting, maintenance, and scaling.

Summary​

EmailEngine ISEmailEngine is NOT
An email API gatewayA mail server
A bridge to existing accountsA service that creates email accounts
Self-hosted softwareA managed cloud service
A unified REST APIA replacement for your email provider

Key Features​

Unified REST API​

Access all email accounts through a single, consistent REST API regardless of the underlying protocol (IMAP, Gmail API, or Microsoft Graph).

Real-time Webhooks​

Receive instant notifications about new emails, email updates, and account changes through webhooks.

OAuth2 Support​

Built-in support for OAuth2 authentication for Gmail, Google Workspace, Microsoft 365, and Outlook.com accounts.

Email Sending​

Send emails through SMTP or native APIs with support for attachments, HTML content, and templates.

Account Management​

Register and manage multiple email accounts with automatic connection handling and reconnection.

Message Management​

  • List, search, and filter messages
  • Mark messages as read/unread
  • Move messages between folders
  • Delete messages
  • Download attachments

AI Agent Access (MCP)​

Serve the Model Context Protocol so AI assistants can search, read, organize and send mail through a curated tool set, using narrowed access tokens rather than mailbox credentials.

Self-hosted​

Run EmailEngine on your own infrastructure for complete control over your email data and privacy.

Use Cases​

  • Email Integration - Add email functionality to your SaaS application
  • Email Automation - Automate email workflows and responses
  • Customer Support - Integrate customer email communications into your CRM
  • Email Analytics - Track and analyze email communications
  • Email Backup - Create backups of email accounts

Quick Start​

Getting started takes five steps:

  1. Install EmailEngine - Download and set up EmailEngine on your server
  2. Configure Redis - Set up Redis for data storage
  3. Register an Account - Add your first email account via API
  4. Set up Webhooks - Configure webhooks to receive notifications
  5. Start Building - Explore the API reference and build your integration

System Requirements​

  • Node.js 20 or newer, and only when running from source. The packaged builds carry their own runtime
  • Redis 6.2 or newer, or a Redis-compatible service such as Upstash; see Redis version
  • Memory 2 GB to evaluate, 4 to 8 GB for production
  • OS Linux, macOS, or Windows

See Installation for the per-platform figures and what drives them.

License​

EmailEngine includes a 14-day free trial with full functionality and no limitations. No credit card is required: the trial is activated from the License page in the admin interface, as described under Free Trial.

For production use, get a license key from postalsys.com.

See Also​