Inboxes, calendars, newsletters, bookings, an AI assistant, and an API for your agents. Everything on your own domain, in one subscription. From $4/mo.

hello@, orders@, support@, across every domain you own. Read and reply from one place, and every reply leaves from the right address.

Fast, private email hosting for you or your business.

Amazing webmail+calendar+contact+files client.

Existing Gmail and Outlook MCP servers route queries through Google/Microsoft APIs. With stalwart-mcp, AI queries hit your Stalwart instance directly. Mail data never leaves your infrastructure; only the AI questions and answers go to the LLM provider.

JMAP is the open protocol that replaces IMAP (and CardDAV and CalDAV). It’s faster, simpler, more powerful, and built for how email works today.

A schema-driven command line tool for administering Stalwart Mail and Collaboration Server over its JMAP API.

The tool fetches the server's schema on first use and derives every command, validation rule, and rendered view from it. The same binary works against any compatible Stalwart deployment without recompilation.

This repository contains Apple's Device Management Client schema data for the MDM (Mobile Device Management) protocol, and the Declarative Device Management feature.

Email Payload reference for mobile config profiles on iOS

Route outgoing SMTP relay messages through Google Stay organized with collections Save and categorize content based on your preferences.​

Self-hosted JMAP webmail for Stalwart Mail Server. Mail, calendar, contacts, and files in one client.

Sieve is a programming language for email filtering. It owes its creation to the CMU Cyrus Project, creators of Cyrus IMAP server.

The language is not tied to any particular operating system or mail architecture. It requires the use of RFC-2822–compliant messages, but otherwise generalizes to other systems that meet these criteria. The current version of Sieve's base specification is outlined in RFC 5228, published in January 2008.

As an administrator, you can customize how email is routed, delivered, and stored to meet your organization's needs.

For example, you might have incoming messages sent to an unknown address routed to a specific mailbox. Or, you might want messages addressed to a specific person automatically also sent to another person. You can have some people get their messages in Gmail and other people get email from your on-premise email server. Gmail can also scan inbound message stored on your on-premise server for spam and compliance.

Gmail split delivery lets you deliver incoming email messages to 2 different email systems in your domain, based on recipients you specify. For example, use split delivery when some people in your organization use Gmail and other people use a different email system.

Set up dual delivery when you need to deliver messages to 2 or more inboxes. For example, users can receive messages in a Gmail inbox and another inbox, for example an inbox on an on-premise email server.

One server for your email, calendars, contacts and shared files, with spam and phishing protection built in. Every standard protocol your clients already speak (JMAP, IMAP, POP3, SMTP, CalDAV, CardDAV and WebDAV) supported natively.

Running mail used to mean stitching together half a dozen separate components (an MTA, a message store, a spam filter, a calendar server, a contacts server, a file server) each with its own configuration quirks. Stalwart collapses all of that into one platform: fewer services to deploy, one configuration to learn, one place to look when something needs attention, and a smaller attack surface.

OPEN SOURCE EMAIL INFRASTRUCTURE for enterprises and high-volume senders

Because KumoMTA is Open Source, we don’t charge for the software — this work is sustained entirely through sponsorships. When you become a sponsor you not only gain access to support and services, you also help power the continued innovation and progress of today’s most advanced email solution.

All prices are per billion messages per year, with no limits on number of servers.

Higher volume senders can contact us for custom pricing.

Mailu is a simple yet full-featured mail server as a set of Docker images. It is free software (both as in free beer and as in free speech), open to suggestions and external contributions. The project aims at providing people with an easily setup, easily maintained and full-featured mail server while not shipping proprietary software nor unrelated features often found in popular groupware.

Main features include:

• Standard email server, IMAP and IMAP+, SMTP and Submission with auto-configuration profiles for clients

• Advanced email features, aliases, domain aliases, custom routing, full-text search of email attachments

• Web access, multiple Webmails and administration interface

• User features, aliases, auto-reply, auto-forward, fetched accounts, managesieve

• Admin features, global admins, announcements, per-domain delegation, quotas

• Security, enforced TLS, DANE, MTA-STS, Letsencrypt!, outgoing DKIM, anti-virus scanner, Snuffleupagus, block malicious attachments

• Antispam, auto-learn, greylisting, DMARC and SPF, anti-spoofing

• Freedom, all FOSS components, no tracker included

Postal is a complete and fully featured mail delivery platform for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready for you to run on your own servers.

Mailpit - email & SMTP testing tool with API for developers

Mailpit is a small, fast, low memory, zero-dependency, multi-platform email testing tool & API for developers.

It acts as an SMTP server, provides a modern web interface to view & test captured emails, and contains an API for automated integration testing (read more).

A comprehensive email domain validation library. Supports DNS, MX, SPF, SMTP, DKIM, DMARC, BIMI, TLSRPT and MTA-STS.

MX record validation SMTP server connection testing DKIM record lookup DMARC policy validation MTA-STS support (RFC 8461) IPv4/IPv6 support Local IP blocking DNS failover resolvers Punycode/IDN support TypeScript support