senn-techSelf-Hosted Mail Server: Stalwart & Axigen vs. Exchange
Exchange has grown over decades — and it shows. A modern mail stack needs less and can do 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.
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. Axigen is the all-rounder for an Exchange replacement with full groupware functionality at complete data sovereignty.