Mox offers a complete mail server stack in a single Go binary requiring no external dependencies. The quickstart command configures a working mail server with SMTP, IMAP4, webmail, and full DNS authentication in under ten minutes. SMTP handling includes a delivery server on port 25, a submission server for authenticated clients, and a queue with automatic retries and DKIM signing. IMAP4rev2 implementation provides full mailbox synchronization with CONDSTORE and QRESYNC for efficient offline clients, NOTIFY for multi-mailbox monitoring, MULTISEARCH across mailboxes, and TLS client certificate authentication via the EXTERNAL SASL mechanism. The built-in webmail provides browser-based reading and composing with message threading, attachments, and HTML rendering without requiring a separate web client. Email authentication implements SPF validation, DKIM signing and verification with automatic key rotation, DMARC policy enforcement with aggregate and failure reporting, DANE with DNSSEC-protected TLSA records, and MTA-STS for certificate verification. Junk filtering combines reputation-based sender scoring with Bayesian content analysis trained per account. The web administration interface manages domains, accounts, DNS records, TLS certificates, delivery queue, and real-time log viewing. Internationalized email addresses with EAI and IDNA support handle non-ASCII domains and mailboxes. Account autoconfiguration publishes settings for Thunderbird autoconfig and Outlook autodiscover. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

With over 13,000 GitHub stars and active monthly releases, Mailcow delivers a production-ready mail server infrastructure through Docker Compose orchestration of twelve integrated containers. The stack pairs Postfix as the MTA handling SMTP traffic with Dovecot for IMAP and POP3 retrieval featuring the Flatcurve full-text search engine, while Rspamd provides machine-learning-powered spam filtering with Bayesian classification, DKIM signing, and ARC support. ClamAV scans attachments for malware including Office document macro analysis via Olefy, and SOGo serves as a responsive webmail client with CalDAV, CardDAV, and Microsoft ActiveSync synchronization. The admin panel manages multiple domains, per-user spam score thresholds, quarantine review, black and whitelists, temporary spam aliases, mailbox quotas, and TLS enforcement policies for both inbound and outbound messages. Security features include two-factor authentication via TOTP, WebAuthn, and Yubikey OTP, a Fail2ban-like Netfilter integration for brute-force protection, and automatic SPF, DKIM, and DMARC configuration. The ACME container handles Let's Encrypt certificate generation with DNS-01 challenge support, while Postfix TLS-Pol provides MTA-STS and DANE/TLSA resolution for encrypted transport. Built-in imapsync enables periodic migration from remote mailboxes, and the REST API allows programmatic management of all server resources. MariaDB stores user data, Redis caches configuration and sessions, and Unbound provides local DNSSEC-validating DNS resolution. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. GPL-3.0 licensed.

Stalwart replaces the traditional Postfix + Dovecot + SpamAssassin + calendar-server stack with one Rust binary that speaks every standard mail and collaboration protocol natively. JMAP, IMAP4rev2, POP3, SMTP, CalDAV, CardDAV, and WebDAV all run inside the same process — no glue scripts, no sidecar daemons, no version conflicts between components. The pluggable storage architecture lets operators choose RocksDB for single-node deployments, FoundationDB for distributed clusters, PostgreSQL, MySQL/MariaDB, or SQLite for the data store, S3/MinIO/Azure Blob for message blobs, and Elasticsearch or Meilisearch for full-text search, with Redis or the internal engine backing rate limiters and session state. Security features include S/MIME and OpenPGP encryption at rest, automated DKIM key generation with DNS publication, DANE and MTA-STS transport security, automatic ACME TLS provisioning, granular ACLs, rate limiting, and IP banning. The browser-based admin console manages accounts, domains, groups, mailing lists, SMTP queues, DMARC/TLS-RPT/ARF reports, and every configuration object without touching a config file, while the self-service portal at /account gives end users password reset and encryption key management. Multi-tenant support with per-tenant quotas enables hosting-platform deployments, and coordinator-less clustering via Zenoh or NATS scales horizontally by adding nodes. Deploy via Docker or the standalone binary. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL v3 licensed.

With 14,000 GitHub stars and 81 releases since March 2023, Stalwart is the most protocol-complete open-source mail server available — delivering JMAP, IMAP4rev2, IMAP4rev1, POP3, SMTP, CalDAV, CardDAV, and WebDAV from a single Rust binary that compiles to a memory-safe, zero-garbage-collection executable with predictable latency under load. The SMTP server implements DMARC, DKIMv2, DKIMv1, SPF, and ARC for complete message authentication with automatic DKIM key rotation, while transport security enforces DANE, MTA-STS, and SMTP TLS reporting to prevent downgrade attacks. Built-in spam filtering with statistical classifiers, DNS blocklists, and collaborative reputation databases eliminates the need for external Rspamd or SpamAssassin deployments. Encryption at rest protects stored messages with S/MIME or OpenPGP, and automatic TLS certificate provisioning via ACME supports TLS-ALPN-01, DNS-01, and HTTP-01 challenges without manual certificate management. The ManageSieve server enables server-side email filtering rules, while full-text search indexes message bodies and attachments for instant retrieval. Pluggable storage backends support RocksDB for embedded deployments, PostgreSQL, MySQL, and S3-compatible object storage for distributed architectures. LDAP and SQL-based authentication integrate with existing directory services, and the web administration panel manages domains, accounts, quotas, and DKIM keys. Security audited with memory safety guaranteed by Rust's ownership model. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

With over 7,100 GitHub stars and 200 contributors since 2016, Mailu has become one of the most popular self-hosted email solutions, delivering a complete production-ready mail server stack as pre-configured Docker containers that eliminate weeks of manual setup. The platform bundles Postfix for SMTP and Submission with auto-configuration profiles for Thunderbird, Outlook, and mobile clients, Dovecot for IMAP and POP3 with full-text search across email attachments, Rspamd for intelligent spam filtering with auto-learn Bayesian classification, greylisting, SPF and DMARC validation, and ClamAV for antivirus scanning of attachments with configurable malicious file blocking. The web administration interface provides global admin controls, per-domain delegation, user quota management, domain aliases, custom routing rules, and announcement capabilities. Users access self-service features including aliases, auto-reply, auto-forward, fetched accounts from external mailboxes via fetchmail, and Sieve filter management through ManageSieve. Security features include enforced TLS on all connections, automatic Let's Encrypt certificate provisioning, outgoing DKIM signing, DANE and MTA-STS support for transport security, and Snuffleupagus PHP hardening for the web interface. The setup wizard at setup.mailu.io generates complete Docker Compose configurations tailored to specific deployment requirements. All components are free and open-source software with zero proprietary dependencies and no tracking. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.