Stalwart proved how clean a modern mail server can be. nextxch goes decisive steps further: a built-in Light/Dark Webmail PWA with 15 color themes, OpenTelemetry & structured logs with live UI, native GoBD WORM, OCR & ZUGFeRD invoice compliance, and 25% to 28% lower per-mailbox licensing.
Capability / Metric
nextxch
Stalwart Enterprise
hMailServer
Postfix + Dovecot + Rspamd
Exchange Online® (Plan 1) / Microsoft 365®
License price (25 to 499 mailboxes)
€1.50 / mailbox / year
€2.00 / mailbox / year
€0 (Discontinued / Legacy)
€0 (high DevOps effort)
approx. €44.40 / yr (Exchange Online® Plan 1 incl. hosting · Microsoft 365® Std. ~€140.40)
Digital Sovereignty & Deployment
100% Self-Hosted (On-Prem, EU Cloud, Container)
100% Self-Hosted (On-Prem / Container)
Windows® On-Prem only
Linux® / multi-container
US Cloud (CLOUD Act) or heavy Exchange® VM
JMAP (RFC 8620/8621) + IMAP4rev2
Both natively integrated
Both natively integrated
(Legacy IMAP4rev1 only)
(No JMAP)
(Proprietary Graph/MAPI)
Groupware: Calendar, Contacts, Notes & Tasks
CalDAV & CardDAV + Mobile Push Sync (WBXML, compatible with ActiveSync® clients)* + IMAP Notes & Tasks + GAL
Native CalDAV & CardDAV (no ActiveSync®-compatible push interface, no built-in Webmail)
No groupware
Requires separate SOGo / Nextcloud
MAPI / Exchange® ActiveSync®
Built-in Webmail PWA + 15 Color Themes
Included (Mail, Calendar, Contacts, Notes, Tasks & WebPush)
Brand/link heuristics, phishing check & reporting in webmail, 69 sending services, IP unblock requests
Spam filter rules (no webmail check)
External spam filters only
Rspamd modules (no webmail integration)
Baseline protection, extended via Defender for Office 365®
Source-Code Escrow & Security Process (RFC 9116)
German Escrow option + Enterprise SLA from Tier 5 (RFC 9116 security process included)
AGPL core + proprietary Enterprise crates
Unmaintained
Open Source
Proprietary cloud SLA
* Legal interoperability notice: The optional WBXML Mobile Push interface (configurable via ActiveSync:Enabled) is an independent clean-room implementation by iqmeta GmbH based on publicly documented interoperability specifications ([MS-ASHTTP]/[MS-ASCMD]/[MS-ASWBXML]) for connecting compatible client devices. Microsoft®, Exchange®, Exchange Online®, ActiveSync®, Outlook®, Microsoft 365®, Windows®, Apple®, iPhone®, and macOS® are registered trademarks of their respective owners. nextxch is neither affiliated with nor endorsed, licensed, or certified by these companies.
Compared to Stalwart Enterprise
Shared Modern Foundations: Both Stalwart and nextxch deliver ESMTP, IMAP4rev2, JMAP, ManageSieve, CalDAV & CardDAV, and OpenTelemetry inside a single modern binary.
Mobile Push Sync (WBXML, compatible with ActiveSync® clients) + IMAP Notes: Stalwart implements CalDAV/CardDAV only (requiring third-party sync apps on Android™). Alongside CalDAV/CardDAV, nextxch provides an independent clean-room WBXML Push interface (compatible with ActiveSync®-capable clients for Mail, Calendar, Contacts, Notes, Tasks, GAL & Out-of-Office; configurable on/off) plus a bidirectional IMAP Notes bridge.
Built-in Webmail PWA incl. Calendar, Contacts, Notes & Tasks: Where Stalwart requires deploying an external webmail stack, nextxch Web PWA ships ready-to-use at /mail/ with zero extra containers.
Purpose-Built for DACH Compliance, MS SQL Server® & Windows Server®: Native Windows® Service with interactive .msi wizard, first-class Microsoft® SQL Server® engine (incl. Express & Azure® SQL), 1-click external port/PTR check, hMailServer direct import, EN 16931 ZUGFeRD/OCR search, and GoBD procedural documentation export.
Compared to hMailServer (Windows®)
Actively Maintained & Modern RFCs: hMailServer is discontinued and lacks JMAP, CalDAV/CardDAV, Passkeys, Ed25519 DKIM, ARC, DANE, and built-in ACME TLS. nextxch runs natively as a Windows® Service without Docker®.
1-Click Direct Import: nextxch natively imports your existing hMailServer Data\*.eml folders, domains, aliases, and distribution lists.
Compared to Postfix + Dovecot + Rspamd + SOGo
One Process (~40 MB Idle RSS) Instead of 9 Daemons: Eliminate fragile socket chains and multi-gigabyte RAM overhead across separate SMTP, IMAP, Sieve, anti-spam, Redis, and webmail containers.
Unified Logs & OpenTelemetry: Manage queues, TraceId-correlated logs, DKIM rotation, CIDR rules, and mailboxes in one cohesive dashboard.
Compared to Exchange Online® & Microsoft 365®
Fair Cost Comparison: Even compared fairly against mail-only Exchange Online® Plan 1 (~€44.40/user/yr incl. cloud hosting), nextxch licensing for 250 mailboxes is €375/yr vs. €11,100/yr, plus only your own VPS or existing server. (Microsoft 365® Business Standard at ~€140.40/yr additionally bundles Office apps & Teams.)
Complete Data Sovereignty: Zero US CLOUD Act exposure: all mail, calendars, contacts, and private keys stay strictly on your own infrastructure.