The modern enterprise mail server. Unified platform. Full sovereignty. 40% lower cost.
SharpMailserver unifies ESMTP, IMAP4rev2, JMAP, ManageSieve, adaptive Anti-Spam, Webmail PWA, GoBD WORM Compliance Archiving, and OCR & ZUGFeRD full-text search in one zero-allocation System.IO.Pipelines engine. Runs natively as a Windows Server Service without Docker, on Linux, macOS, NAS, and Kubernetes starting at €1.20 per mailbox per year.
// Integrierte Transactional HTTP API mit Idempotency-Key & Dual-DKIMusing var http = new HttpClient { BaseAddress = new("https://mail.iqmeta.de") };
http.DefaultRequestHeaders.Add("X-Api-Key", Environment.GetEnvironmentVariable("SHARPMAIL_KEY"));
http.DefaultRequestHeaders.Add("Idempotency-Key", "inv-2026-0841");
var res = await http.PostAsJsonAsync("/api/v1/send", new {
from = "billing@iqmeta.de",
to = new[] { "accounting@customer.de" },
subject = "ZUGFeRD Invoice #2026-0841",
htmlBody = "<p>Please find your EN 16931 invoice attached.</p>"
});
# RFC 5228 Sieve: editierbar per ManageSieve (Port 4190) oder Visual Rule Builderrequire ["fileinto", "vacation", "reject"];
if header :contains "X-ZUGFeRD-Detected""true" {
fileinto"Archive/Invoices-2026";
stop;
}
Live in 60 seconds
Zero config-file jungle. Run natively as a Windows Service, Linux daemon, or container.
Traditional mail stacks force you to glue together Postfix, Dovecot, Rspamd, OpenDKIM, Certbot, Redis, and a legacy PHP webmail client. SharpMailserver ships every protocol, Webmail PWA, Admin Cockpit, Transactional Send API, and 0 ms SNI Let's Encrypt automation inside one cohesive, memory-safe service.
Engineered for throughput, zero-trust security, and compliance
Every protocol parser, spam filter, and storage engine is engineered from the ground up with strict memory bounds and 100% central exception telemetry.
Zero-Alloc System.IO.Pipelines
ESMTP (CHUNKING/BDAT), IMAP4rev2 (< 5 ms IDLE push) & JMAP (RFC 8620/8621) stream with flat memory (~58 MB idle) and strict DoS guards.
Complete Email Cryptography
SPF, Dual-DKIM (Ed25519 + RSA-2048 with 1-click key rotation), DMARC, ARC chain sealing, MTA-STS, TLS-RPT, DANE (TLSA), and OutboundGuard.
GoBD WORM, ZUGFeRD & OCR Search
Immutable S3 Object Lock (COMPLIANCE), Legal Hold, read-only Auditor role without mutating \Seen flags, plus native ZUGFeRD/PDF & scan OCR indexing.
Webmail PWA, 15 Themes & 5s Mobile QR
Compact Admin UI & Webmail in VS Code Dark Grey with 15 selectable accent themes each, VAPID WebPush, and PKCS#7-signed Apple .mobileconfig QR setup.
Passkeys, 2FA, OIDC & SCIM 2.0
FIDO2/WebAuthn Passkeys, strictly enforced 2FA + per-device App Passwords across all TCP ports, plus enterprise SSO (OIDC) and SCIM 2.0 provisioning.
1-Click hMailServer & IMAP Migration
Direct import of existing Windows hMailServer installations (domains, accounts, aliases, Data\*.eml) plus zero-downtime live TLS IMAP delta sync.
Real live interfaces from the server
Compact Admin Cockpit, GoBD Archive & SharpMail Webmail built right in
Both the high-density Admin & GoBD Cockpit and the SharpMail Webmail PWA are built right in: styled in neutral VS Code Dark Grey or crisp Light Mode, each with 15 independently selectable color themes.
https://mail.sharpmailserver.com/admin/ · Dark Theme1440 x 900 @ 2x
Admin & GoBD Cockpit (VS Code Dark Grey): High-density real-time telemetry, 15 selectable color themes, deduplicated Zstd Hybrid storage metrics, and live SMTP queue.See all UI & server capabilities
Database Architecture & Document Intelligence
PostgreSQL or SQLite WAL paired with sub-millisecond OCR, PDF & ZUGFeRD search
SharpMailserver cleanly separates transactional metadata from content-addressed blobs and automatically indexes PDFs, EN 16931 e-invoices, and scanned image attachments in the background.
Relational Metadata & Hybrid SHA-256 Zstd Blob Store
PostgreSQL für Enterprise-Cluster: Optimized B-tree and GIN full-text indexes, read replicas, and multi-node high availability for tens of thousands of mailboxes on self-managed PostgreSQL, AWS RDS, Azure, or Cloud SQL.
SQLite im WAL-Modus für Single-Server & NAS: Zero-administration single-node operation with built-in FTS5 trigram indexing. Ideal for Windows Services, Proxmox LXC containers, NAS systems, and branch servers.
Globale SHA-256-Deduplizierung + Zstandard: A 20 MB attachment sent to 40 internal recipients is stored physically once with Zstandard compression, cutting disk and S3 storage consumption by 55% to 62%.
Revisionssicherer S3 Object Lock (WORM): Hybrid tiering caches hot messages on local NVMe flash while locking long-term compliance archives immutably in S3-compatible object storage.
3-Stage Full-Text, ZUGFeRD & OCR Search Pipeline
Finds invoice IDs, contracts & scanned paper receipts in < 8 ms
Stufe 1 (Echtzeit-MIME & Header-Index): Headers, participants, Message-IDs, and normalized text/HTML bodies become searchable at the exact millisecond of delivery across Webmail, JMAP, and IMAP SEARCH.
Stufe 2 (Natives PDF, Office & ZUGFeRD / XRechnung): Natively extracts multi-page PDF text, DOCX/XLSX documents, and structured EN 16931 e-invoice XML fields (invoice numbers, IBANs, VAT IDs, line items, totals).
Stufe 3 (Asynchrone OCR-Texterkennung für Scans): Scanned paper mail, photographed receipts, and image-only PDFs (PNG, JPEG, TIFF, scanned PDFs) are processed asynchronously by an isolated OCR worker queue for full-text discovery.
GoBD-Prüfer-Suche ohne Veränderung: Tax auditors search across mail bodies, ZUGFeRD XML, and OCR-indexed scans in strict read-only mode without ever altering user \Seen flags.
Verified Benchmarks & Resource Footprint
Minimal memory footprint. Predictable high throughput under load.
Built on zero-copy network pipelines, pooled memory buffers, and strict pre-allocation caps, SharpMailserver keeps RAM flat and predictable even under heavy concurrency.
Microsoft Exchange Server On-Premises8.192 MB bis 16.384+ MB RAM
Operating Systems, Kubernetes & Cloud Ecosystem
Runs everywhere: Native Windows Service, Linux, macOS, Kubernetes, Hyperscalers & EU Clouds
Total deployment freedom with zero vendor lock-in: run natively as a Windows Service or Linux daemon without Docker, on macOS Apple Silicon, in Kubernetes, or on any global hyperscaler or sovereign European cloud.
Native Operating Systems (No Docker Needed)
First-class native system daemons for both x86_64 and ARM64 architectures:
Windows Server 2019 / 2022 / 2025 (Service) Debian / Ubuntu LTS (systemd) RHEL / AlmaLinux / Rocky / SUSE macOS (Apple Silicon M1-M4 & Intel, launchd) Raspberry Pi OS (ARM64)
Kubernetes & Container Runtimes
OCI-compliant multi-arch images with /healthz probes, /metrics for Prometheus & PROXY protocol v2:
Kubernetes & Helm ChartsDocker & Docker ComposePodman (Rootless)containerd & CRI-ORed Hat OpenShiftSUSE Rancher & K3sHashiCorp NomadProxmox VE (LXC & KVM)
Global Hyperscalers & Sovereign EU Clouds
Validated with managed PostgreSQL, TCP load balancers, and immutable S3/Blob storage across:
Design and audit perfect DNS & Reverse DNS records in seconds
Mismatched PTR records, broken SPF chains (> 10 DNS lookups), or missing DMARC alignment are the #1 cause of rejected mail at Gmail and Microsoft. Inspect any live domain or generate a complete zone including IPv4 in-addr.arpa and 32-nibble IPv6 ip6.arpa PTR records.
Domain, IP & Policy Configuration
Generates complete DNS and reverse DNS records with live inspection
Ready-to-run guides for Windows Service, Proxmox, NAS, Raspberry Pi & European hosters
Whether deploying as a native Windows Service without Docker, on a Synology/UGREEN/Unraid NAS, or on a VPS at Hetzner, netcup, IONOS, Strato, ALL-INKL, Hostinger, or OVHcloud: pick your target below for exact commands and rDNS settings.
* Progressive bracket billing (identical to Stalwart's model, at 40% lower rates): e.g. 600 mailboxes pay Tier 1 (€1.20 per mailbox per year) on the first 499 and Tier 2 (€1.02 per mailbox per year) on the remaining 101. Only user and group mailboxes count. Domains, tenants, aliases, mailing lists, and servers are unlimited at €0. Prices exclude VAT.
Interactive License Estimator
Annual Total: SharpMailserver Enterprise
€300 per year
approx. €25 per month
Savings vs. Stalwart Enterprise:€200 per year (-40%)
Savings vs. Microsoft 365:€34,800 per year
Premium Engineering Support included (150+ mailboxes)