Best Self Hosted Alternatives to Proton Mail Professional

Mail-in-a-Box is a turnkey project that turns a fresh Ubuntu server into a complete, working email system with the surrounding services needed for deliverability and day-to-day administration. It aims to make running your own mail service practical by installing and configuring a curated, integrated stack.

Key Features

• SMTP and IMAP mail services with integrated webmail
• Web-based control panel to manage users, aliases, domains, DNS records, and backups
• Automated DNS setup (when used as authoritative DNS) including common deliverability and security records
• Automatic TLS certificate provisioning and renewal for mail and web services
• Built-in spam mitigation (filtering and greylisting) and mail filtering rules support
• Daily health checks and monitoring focused on mail service correctness (ports, DNS, certificates)
• Optional contacts and calendar sync services integration
• RESTful API for control-panel actions

Use Cases

• Hosting email for multiple users across one or more personal or small-organization domains
• Replacing a hosted mail provider while retaining standard IMAP/SMTP compatibility
• Running an “email appliance” on a VPS with automated security and deliverability checks

Limitations and Considerations

• Designed to be minimally configurable; advanced customization and post-install tweaking are intentionally limited
• Email deliverability can still be affected by external provider policies and IP reputation

Mail-in-a-Box is best suited for individuals and small teams that want a straightforward, integrated mail stack with sane defaults and an admin UI. It combines core mail protocols with the operational pieces (DNS, TLS, monitoring, backups) that are typically the hardest parts to get right.

mailcow: dockerized is an integrated mail server suite packaged as a set of Docker containers. It combines core mail components (SMTP/IMAP) with a web-based administration interface to manage domains, mailboxes, and security features.

Key Features

• Containerized stack managed via Docker Compose for reproducible deployments
• SMTP delivery with Postfix and IMAP access via Dovecot
• Webmail and groupware via SOGo
• Built-in spam filtering with Rspamd and antivirus scanning with ClamAV
• ACME/Let’s Encrypt certificate automation for TLS
• Web admin UI for domains, aliases, mailboxes, and access controls (ACL)

Use Cases

• Self-managed mail hosting for individuals, families, and organizations
• All-in-one email platform for small businesses needing webmail and groupware
• Homelab mail server with integrated spam/virus protection and TLS automation

Limitations and Considerations

• Operating a mail server requires careful DNS and deliverability configuration (SPF/DKIM/DMARC, rDNS) and ongoing maintenance
• Resource usage can be higher than minimalist MTAs due to multiple bundled services

mailcow: dockerized provides a cohesive, production-oriented mail stack with a unified management experience. It is well-suited for administrators who want an integrated suite rather than assembling and maintaining separate mail components.

Stalwart Mail Server is an all-in-one mail and collaboration server built to provide a modern, standards-based alternative to assembling multiple separate components. It combines email delivery and storage, groupware protocols, and built-in security controls in a single, scalable service written in Rust.

Key Features

• Multi-protocol email support including SMTP, IMAP4, POP3, and JMAP
• Collaboration protocols including CalDAV, CardDAV, and WebDAV for calendars, contacts, and file storage
• Integrated spam and phishing defenses, including filtering rules, DNS blocklists, greylisting, and a statistical classifier
• Email authentication and transport security features such as DKIM, SPF, DMARC, ARC, MTA-STS, DANE, and TLS reporting
• Flexible backends for storage and search, with support for multiple databases and optional external search engines
• Built-in web-based administration with real-time stats, queue management, reporting views, and log exploration
• Authentication options including LDAP, SQL, and OpenID Connect, plus roles/permissions and ACLs
• Observability via logging/tracing and metrics integrations, with webhook-based event automation

Use Cases

• Replace a traditional MTA + IMAP store + spam filter stack with a single integrated platform
• Run a domain email service with modern clients via JMAP while retaining IMAP/POP3 compatibility
• Provide calendars, contacts, and file sharing for teams using CalDAV/CardDAV/WebDAV

Limitations and Considerations

• Some advanced scaling and backend options can add operational complexity compared to small single-node deployments

Stalwart Mail Server is well-suited for organizations and individuals who want a secure, standards-compliant email and collaboration platform with modern protocols, integrated protection against abuse, and deployment flexibility from small setups to large clustered environments.

Mailu is a simple yet full-featured email server distributed as a set of Docker images. It provides the core protocols needed to run your own mail infrastructure, plus webmail and an administration interface.

Key Features

• SMTP, Submission, IMAP/IMAP+, and optional POP3 support
• Multiple webmail options and a built-in administration UI
• Aliases, domain aliases, custom routing, auto-forward and auto-reply
• Fetched accounts (fetchmail-style) and ManageSieve support
• Per-domain delegation, global admins, announcements, and mailbox quotas
• Security features including enforced TLS, Let’s Encrypt integration, outgoing DKIM, DMARC/SPF, and anti-spoofing options
• Anti-spam features such as greylisting and auto-learning, plus optional antivirus scanning

Use Cases

• Hosting email for personal domains or small organizations with a web-based admin panel
• Running multi-domain mail hosting with delegated per-domain administration
• Deploying a containerized mail stack with DKIM/DMARC/SPF and spam filtering

Limitations and Considerations

• Deliverability depends on correct DNS configuration (SPF, DKIM, DMARC, rDNS) and IP reputation
• Operating a mail server requires ongoing maintenance (TLS, spam rules, storage quotas, and monitoring)

Mailu focuses on providing a complete, containerized mail stack using standard components rather than a full groupware suite. It is designed to be straightforward to deploy and maintain while offering the security and administrative features expected from a modern mail server.

iRedMail is a packaged, open-source mail server solution that automates deployment and integration of standard mail components on mainstream Linux and BSD distributions. It combines mail transport, delivery, webmail/groupware and anti-spam/antivirus tooling into a reproducible installer and offers optional commercial admin/enterprise editions for extra features and support. (iredmail.org)

Key Features

• Automated installer that configures Postfix as MTA and Dovecot for IMAP/POP3 delivery, including secure defaults (TLS, modern password hashing). (github.com)
• Pluggable backends: supports OpenLDAP and SQL backends including MySQL/MariaDB and PostgreSQL for account storage and policies. (iredmail.org)
• Webmail and groupware options: Roundcube webmail and SOGo groupware (CalDAV/CardDAV/ActiveSync) can be deployed as part of the stack. (iredmail.org)
• Anti-spam and antivirus integration: built-in support for SpamAssassin/Rspamd-style filtering, ClamAV, SPF/DKIM/DMARC and quarantining workflows. (docs.iredmail.org)
• Optional web admin panels and commercial tiers: free iRedAdmin (basic), paid iRedAdmin‑Pro with extended features and an online demo for evaluation. (iredmail.org)
• Multiple deployment options and tooling: documented for several mainstream distros (Debian, Ubuntu, Red Hat/CentOS/Rocky/AlmaLinux) and an official dockerized edition is available. (github.com)

Use Cases

• Small-to-medium organizations wanting a self-hosted, privacy-focused mail server with modern mail standards and webmail access.
• Service providers or admins migrating legacy Exchange/hosted systems to an integrated open-source mail stack.
• Teams requiring integrated calendar/contacts (CalDAV/CardDAV/ActiveSync) and per-domain administration via a web panel.

Limitations and Considerations

• Backend choice (OpenLDAP or SQL) is selected at install time and is not trivially switchable after installation; migrating backends requires planned data migration. (forum.iredmail.org)
• Some advanced management features (iRedAdmin‑Pro) and enterprise conveniences are paid; community edition covers core mail functionality but lacks Pro panel features out of the box. (iredmail.org)
• Certain components (notably SOGo groupware) increase resource requirements significantly (larger memory/CPU for ActiveSync/large user bases). (docs.iredmail.org)

In summary, iRedMail is a mature, opinionated integration of proven open-source mail components that simplifies deploying a secure, standards-compliant mail server across mainstream Linux/BSD systems while providing paid options for enhanced management and support. (iredmail.org)

Cyrus IMAP is a long-running, production-grade server for hosting email along with contacts and calendars. It focuses on security and scalability by keeping mailboxes in server-managed storage and exposing access via standard protocols.

Key Features

• IMAP and JMAP support for mailbox access
• CalDAV and CardDAV support for calendars and contacts
• POP3, NNTP, and WebDAV protocol support (deployment-dependent)
• Mailbox ACLs and quota management for multi-user environments
• Replication and “Murder” aggregation for large and distributed setups
• Flexible server-side mail filtering via Sieve
• Search capabilities (with optional components depending on build)
• Extensive authentication options via Cyrus SASL
• Integrations for antivirus and antispam toolkits
• Deliverability-related support for SPF, DKIM, and DMARC (typically via integration with surrounding mail stack)

Use Cases

• Hosting IMAP/JMAP mailboxes for an organization where users do not need shell access
• Providing CalDAV/CardDAV services for groupware-style deployments
• Building a scalable mail backend for service providers or large enterprises

Limitations and Considerations

• A full email system typically requires integration with an MTA and additional components for webmail, spam filtering, and DKIM signing

Cyrus IMAP is well-suited to administrators who need a robust standards-based messaging platform with strong performance characteristics and operational controls. It is commonly used in demanding environments where scalability, manageability, and protocol support are priorities.

Simple NixOS Mailserver is a set of NixOS modules that helps you declaratively run a complete mail server on NixOS. It aims to provide a reasonably secure, maintainable setup for hosting email domains with a reproducible Nix configuration.

Key Features

• Declarative NixOS configuration for end-to-end mail server deployment
• SMTP service with modern TLS and authentication options
• IMAP mail access for user mailboxes
• Spam filtering integration and common email hygiene features
• Email authentication support (DKIM, DMARC, SPF)
• Optional webmail support depending on chosen configuration
• Designed to fit naturally into NixOS system management and upgrades

Use Cases

• Self-hosting email for a personal domain on NixOS
• Running mail for small organizations that want reproducible infrastructure
• Homelab mail setups with strong control over configuration and updates

Limitations and Considerations

• Intended for NixOS; not a general-purpose mailserver installer for other distributions
• Deliverability depends on DNS correctness and IP reputation, which must be managed externally

Simple NixOS Mailserver is best suited to users who want an opinionated but flexible email stack managed entirely through NixOS. It provides building blocks for a complete mail system while keeping configuration reproducible and auditable.

Zimbra Collaboration is an enterprise collaboration and messaging platform that provides email, webmail, calendaring, contacts, and related groupware capabilities. It is commonly deployed by organizations that need an on-prem or private-cloud alternative to hosted suites.

Key Features

• Full-featured webmail client with conversation views, search, folders, tags, and attachments
• Calendar and scheduling with shared calendars, resource/room scheduling, and free/busy
• Contacts with address books, distribution lists, and global address list (directory integration)
• IMAP/POP/SMTP support for desktop/mobile mail clients
• Admin console for domain/account provisioning, quotas, policies, and monitoring
• Built-in anti-spam/anti-virus integration options and mail-flow controls (e.g., policies, routing)
• Backup/restore and delegation/sharing features (edition-dependent)

Use Cases

• Replace hosted email/collaboration suites for businesses, schools, and public-sector orgs
• Provide multi-domain email hosting with centralized administration and policy control
• Offer webmail + CalDAV/CardDAV-style groupware experience for mixed client environments

Limitations and Considerations

• Some capabilities (e.g., advanced backup, mobile sync/EAS, HA tooling) may depend on the specific Zimbra edition and installed add-ons
• Operating and upgrading a full mail stack requires careful DNS/TLS, deliverability, and storage planning

Zimbra is suited to organizations needing a mature, admin-friendly groupware platform with broad client compatibility and a rich web UI. Its modular server components and administrative tooling make it a common choice for enterprise-grade self-managed email and collaboration deployments.

b1gMail is a web-based email and collaboration suite designed to let organizations run their own hosted email services. It provides webmail, groupware features and an administration control panel for managing users, domains and server integrations.

(b1gmail.eu)

Key Features

• Full-featured webmail interface with HTML5 features (drag & drop for emails and attachments) and modern UI components.
• Groupware: address book, calendar, tasks/todo lists, notes and a cloud drive integrated into the web UI.
• Administration Control Panel (ACP) for multi-tenant administration, user/group management and setup wizards.
• Extensible plugin system allowing installation of additional features via plugins without modifying core code.
• Spam and virus protection including DNS blacklist filtering, a trainable Bayesian spam filter and ClamAV integration for virus scanning.

(b1gmail.eu)

Use Cases

• Hosting providers or organizations that want to offer branded hosted email and groupware to customers or internal users.
• Small-to-medium organizations needing an integrated webmail, calendar and file drive solution with centralized admin controls.
• Service operators who want an extendable webmail portal with plugin support and configurable filtering/antivirus pipelines.

Limitations and Considerations

• Server requirements and compatibility: recent releases document minimum PHP and database requirements (PHP version constraints and recommended MariaDB; MySQL 8.x has known compatibility issues). Plan platform versions accordingly when deploying or upgrading.
• Third-party components: the product historically uses CKEditor in its web UI (CKEditor 4 was noted as EOL for older releases), and some legacy commercial plugins may be incompatible with newer OSS releases.
• Repository access note: attempts to fetch the Codeberg repository at the provided URL were blocked by robots.txt; documentation and release notes are available on the official site and support pages, and the b1gMailServer add-on has a referenced GitHub mirror for its server component.

(b1gmail.eu)

b1gMail is geared toward operators who need an integrated webmail and groupware portal with administrative controls and extensibility. It is a mature product with documented installation guides, admin manuals and plugin development guidance for deploying and customizing hosted email services.

(b1gmail.eu)