senn-techSelf-Hosted Mail Server: Stalwart & Axigen vs. Exchange
Exchange has grown over decades — and it shows. A modern mail stack carries less ballast and still covers more. We’ve used Stalwart and Axigen in practice and compare them honestly.
Exchange: When Still Makes Sense?
If the company is deeply invested in M365 and Outlook/MAPI calendar integration is non-negotiable, Exchange is hard to avoid. In all other scenarios, Exchange is an overloaded system with burdensome maintenance, CU patches, and CAL licensing.
Stalwart: Rust-Based Newcomer
Stalwart Mail Server is written in Rust, brings JMAP in addition to IMAP and SMTP, and runs as a single binary. This is no longer futuristic experimentation — Stalwart is production-ready.
stalwart-mail --config /etc/stalwart/config.toml
JMAP is the decisive advantage: a modern, JSON-based protocol that leaves IMAP’s limitations behind. Push, no polling. Structured data instead of header parsing.
Axigen: The All-Rounder
Axigen brings groupware features reminiscent of Exchange: calendar, contacts, tasks — all via ActiveSync, CalDAV, CardDAV. Administration is web-based and clean. Axigen has run stably for years, and its licensing model is transparent.
Direct Comparison
| Criterion | Stalwart | Axigen | Exchange |
|---|---|---|---|
| Base | Rust, single binary | dedicated, web-admin | evolved, complex |
| Protocols | JMAP, IMAP, SMTP | IMAP, ActiveSync, Cal/CardDAV | MAPI, EAS, IMAP |
| Groupware | Mail-focused | full (calendar/contacts) | full |
| License | Open Source | transparent | CAL / M365 |
| Data Sovereignty | complete | complete | with provider |
| Ideal for | modern lean stack | Exchange replacement with groupware | deep M365 integration |
The Calculation
Exchange-M365 costs add up per mailbox per month. A self-hosted mail server with Stalwart or Axigen pays for itself at mid-sized installations within a year. Added benefit: data sovereignty — emails never leave the premises.
Our Setup
We combine Stalwart (SMTP/IMAP) with NoSpamProxy as a mail gateway in front. This yields a clean, maintainable stack with full control. How we grow this into a full, EU-hosted mail stack with a modern webmail layer, we describe in our piece on Bulwark, Stalwart & PMG.
Further Reading
When is Exchange still the right choice?+
Only when the company is deeply invested in M365 and Outlook or MAPI calendar integration is non-negotiable. In all other scenarios, Exchange is an overloaded system with burdensome maintenance, CU patches, and CAL licensing. Modern self-hosted alternatives like Stalwart and Axigen offer IMAP and SMTP at a fraction of the complexity.
What is the decisive advantage of Stalwart Mail Server?+
Stalwart is written in Rust, runs as a single binary, and brings the modern JMAP protocol alongside IMAP and SMTP. JMAP is JSON-based, offers push instead of polling, and processes structured data instead of header parsing. Stalwart is production-ready and ideal for a modern, lean mail stack with complete data sovereignty – emails never leave the premises.
When is Axigen the better alternative to Exchange?+
When groupware features like calendar, contacts, and tasks are wanted, reminiscent of Exchange. Axigen delivers those via ActiveSync, CalDAV, and CardDAV, with web-based and clean administration. It has run stably for years, and its licensing model is transparent. If you want an Exchange replacement with full groupware scope and have to keep data in-house, Axigen is the right fit.