#smtp + #open-source

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.