Stalwart
Open SourceOpen-source mail & collaboration server with JMAP, IMAP, SMTP and anti-spam
AI Summary
Stalwart is an open-source mail and collaboration server developed in Rust that combines MTA, message store, anti-spam, calendar and contacts in a single application. The tool supports modern protocols like JMAP as well as IMAP, SMTP, CalDAV and CardDAV with comprehensive security features. It is designed for businesses that need a scalable, secure and easy-to-manage email infrastructure.
✓ Pros
- +All-in-one solution without complex integration of multiple components
- +Developed in Rust for high memory safety and performance
- +Comprehensive security features with encryption, DANE, MTA-STS and ACME
✗ Cons
- −Relatively new to the market with a smaller community than established alternatives
- −Setup and migration require technical know-how for complex mail infrastructures
Use Cases
- →Operating a company-owned email infrastructure with modern protocols
- →Self-hosted collaboration platform with calendar, contacts and file sharing
- →Spam and phishing protection with DMARC, DKIM, SPF and integrated filtering
- →Scalable mail server solution for millions of mailboxes with load balancing
Who is it for?
Ideal for system administrators, IT teams and businesses looking for a modern, secure and scalable self-hosted email and collaboration solution.
Tags
What is Stalwart?
Stalwart is an open-source mail and collaboration server written in Rust that combines MTA, message store, anti-spam, calendar and contacts into a single application. Instead of chaining multiple specialized services, Stalwart delivers everything from one process. Supported protocols include JMAP, IMAP, SMTP, CalDAV and CardDAV. For securing mail traffic, DMARC, DKIM, SPF, DANE, MTA-STS and automatic certificate management via ACME are all built in. Stalwart is aimed at teams that want to run their own email infrastructure without maintaining a collection of interdependent components.
Core features
- Protocol support: JMAP as a modern API protocol alongside classic standards such as IMAP and SMTP.
- Collaboration features: Calendar (CalDAV) and contacts (CardDAV) are directly integrated, no external addition required.
- Anti-spam and email authentication: Built-in filtering combined with DMARC, DKIM and SPF validation.
- Transport encryption and certificates: DANE, MTA-STS and ACME support without manual certificate management.
- Scalability: The architecture supports load balancing and is described by the project as designed for millions of mailboxes.
Who is Stalwart for?
The target audience is system administrators and IT teams that self-host a complete mail stack. Anyone who has previously combined Postfix, Dovecot and a separate anti-spam service will find Stalwart an alternative that requires less integration effort. Getting started requires solid DNS knowledge and experience with mail infrastructure. Anyone who has never operated an MTA will struggle with configuring SPF, DKIM and DANE first, regardless of how the tool itself is structured.
Context & alternatives
Stalwart belongs to the category of self-hosted mail servers. Established alternatives with larger communities are Mailcow (Docker-based, combining Postfix and Dovecot) and iRedMail. Both have longer project histories and more documented production deployments. Stalwart's distinguishing factor is its monolithic architecture as a single Rust binary and its native JMAP implementation. For those who want to use JMAP with modern mail clients in production, comparable open-source options are scarce.
