Tuta Mail

Best Self Hosted Alternatives to Tuta Mail

A curated collection of the 16 best self hosted alternatives to Tuta Mail.

Encrypted email and calendar service providing end-to-end encryption, secure contacts management, and privacy-focused features. Offers web, desktop, and mobile clients and supports optional custom domains for secure email and calendaring.

Alternatives List

#1
docker-mailserver

docker-mailserver

Production-ready mail server stack in a Docker container with SMTP, IMAP/POP3, LDAP auth, anti-spam/AV, DKIM/DMARC, and optional OAuth2 support.

docker-mailserver screenshot

docker-mailserver (DMS) is a production-ready, containerized email server appliance that bundles common mail components into a single Docker image. It is designed to be “full stack but simple”, emphasizing file-based configuration (no SQL database) to keep setups easy to version, deploy, and upgrade.

Key Features

  • SMTP server with Postfix
  • IMAP and POP3 server with Dovecot
  • Optional LDAP-backed authentication (including SASL)
  • Anti-spam stack integration (including Rspamd and SpamAssassin options)
  • Antivirus scanning with ClamAV
  • Email authentication protections with DKIM and DMARC support
  • Abuse and brute-force mitigation via Fail2ban and Postscreen
  • TLS certificate support including Let’s Encrypt, as well as manual/self-signed certificates
  • Included maintenance and administration helper script (setup.sh)

Use Cases

  • Self-hosting mail for a personal domain or homelab with a Docker-based workflow
  • Running small-to-medium organization mail services with common anti-spam and security components
  • Providing a reproducible, version-controlled mailserver configuration for teams and environments

Limitations and Considerations

  • Mail hosting requires careful DNS and deliverability configuration (SPF, DKIM, DMARC, rDNS) and ongoing monitoring to avoid delivery issues
  • Advanced customization may require inspecting the running container or using startup patch scripting for overrides

docker-mailserver is a practical option when you want a complete mail stack in a single container while retaining transparent, file-based configuration. It aims to reduce operational complexity without hiding the underlying building blocks that power a standard email system.

17.7kstars
2kforks
#2
Mail-in-a-Box

Mail-in-a-Box

Mail-in-a-Box is a one-click mail server appliance for Ubuntu, bundling SMTP/IMAP, webmail, DNS, TLS automation, backups, and an admin control panel.

Mail-in-a-Box screenshot

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.

15.1kstars
1.5kforks
#3
mailcow: dockerized

mailcow: dockerized

Mailcow is a dockerized mail server suite providing SMTP/IMAP, webmail, anti-spam/anti-virus, and domain/mailbox administration via a unified web UI.

mailcow: dockerized screenshot

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.

11.9kstars
1.6kforks
#4
Stalwart Mail Server

Stalwart Mail Server

All-in-one open-source mail and collaboration server with SMTP, IMAP, JMAP, CalDAV, CardDAV, and WebDAV, plus integrated anti-spam and phishing protection.

Stalwart Mail Server screenshot

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.

11.2kstars
602forks
#5
Mailu

Mailu

Mailu is a full-featured mail server distributed as Docker images, providing SMTP/IMAP/POP3, webmail, administration UI, and built-in security and anti-spam features.

Mailu screenshot

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.

7kstars
960forks
#6
Maddy Mail Server

Maddy Mail Server

Go-based, modular mail server implementing SMTP/LMTP/IMAP with built-in DKIM/SPF/DMARC, storage backends (SQLite/Postgres/S3), Prometheus metrics and Docker support.

Maddy Mail Server screenshot

Maddy is a composable, single-daemon mail server written in Go that implements SMTP (MTA), SMTP/LMTP (MX/Submission) and IMAP access. It includes built-in mail security protocols (DKIM, SPF, DMARC, DANE, MTA-STS), ACME certificate handling and OpenMetrics/Prometheus telemetry, aiming to replace multiple traditional components with a unified configuration and low maintenance surface. (maddy.email)

Key Features

  • Integrated mail stack: send and receive mail (MTA/MX) and provide mailbox access (IMAP/LMTP) from one daemon; IMAP storage is explicitly marked as beta. (maddy.email)
  • Built-in security: DKIM signing and verification, SPF checks and DMARC handling plus support for DANE and MTA-STS.
  • Flexible storage: filesystem blob store and S3-compatible blob backend; SQL-indexed IMAP storage supports SQLite, PostgreSQL and CockroachDB. (maddy.email)
  • Observability & ops: OpenMetrics/Prometheus endpoint, ACME-based automatic certificate management, prebuilt tarballs and an official Docker image for deployment. (maddy.email)
  • Integrations and extensions: designed to interoperate with Dovecot, rspamd, Mailman and external SMTP targets; modular pipeline for checks, signing and routing.
  • Developer & build: Go-based codebase using Go modules; release notes document build/tooling requirements for modern Go toolchains. (github.com)

Use Cases

  • Self-hosted mail for individuals or small teams who want an all-in-one MTA+IMAP server with security defaults.
  • Consolidating mail delivery and filtering pipelines to reduce the number of separate services (Postfix/Dovecot/OpenDKIM/etc.) to a single configurable daemon.
  • Containerized or VPS deployments where observability (Prometheus) and S3/backed storage are desirable.

Limitations and Considerations

  • IMAP storage is labelled as "beta" in the project documentation; users requiring mature, feature-rich IMAP implementations are advised to consider pairing maddy with established IMAP servers (e.g., Dovecot) for production IMAP feature parity. (maddy.email)
  • SQLite-based storage has write-locking characteristics and checkpoint/vacuum considerations that can limit parallel write throughput; larger or high-concurrency deployments should use a server-grade RDBMS (Postgres/CockroachDB). (maddy.email)

Maddy provides a compact, security-focused mail server alternative that centralizes mail delivery, storage and protocol handling into a single Go daemon. It is well suited for users who prefer an integrated, modular approach but should be evaluated carefully against workload, IMAP feature needs and storage concurrency requirements.

5.8kstars
306forks
#7
emailwiz

emailwiz

A Bash script that auto-implements a full mail server (Postfix, Dovecot, DKIM, SpamAssassin) with TLS and PAM-based logins on Debian/Ubuntu.

emailwiz screenshot

emailwiz is a Bash-based installer for Debian/Ubuntu that automatically deploys a complete mail server stack comprising Postfix, Dovecot, SpamAssassin, and OpenDKIM, with TLS via Certbot. It configures PAM-based logins and security features like fail2ban.

Key Features

  • Automates installation and configuration of Postfix, Dovecot, SpamAssassin, OpenDKIM, and Certbot TLS
  • Links Postfix and Dovecot securely with native PAM log-ins
  • Includes fail2ban for server security
  • Provides guidance and finishing steps for DNS records (MX, SPF, DMARC, DKIM)
  • Offers an isolated/self-signed certificate option for private environments
  • Targets Debian/Ubuntu as the operating system

Use Cases

  • Deploy a standalone mail server for a small business or home lab on Debian/Ubuntu
  • Set up DKIM, SPF, DMARC and TLS to improve email deliverability
  • Rapid provisioning of a mail server with minimal manual configuration

Limitations and Considerations

  • No graphical webmail interface is installed by default; a mail client is expected
  • DNS configuration is required (MX, SPF, DMARC, DKIM) for proper deliverability
  • An isolated/self-signed certificate mode exists but will not work for public mail delivery
  • The project emphasizes UNIX user accounts (no SQL database)

Conclusion

emailwiz provides an automated, script-driven path to a secure, mail-server setup on Debian/Ubuntu, reducing manual configuration and ensuring standard mail components and DKIM/TLS are in place. It is linked from the author’s site and maintained as a Bash script intended for self-hosted deployments. (github.com)

2.1kstars
337forks
#8
WildDuck

WildDuck

WildDuck is a horizontally scalable IMAP/POP3 mail server that stores all mail in MongoDB, runs stateless Node.js workers, and provides a REST API for full server control.

WildDuck screenshot

WildDuck is a modern IMAP/POP3 mail server designed for large-scale deployments. It stores all mail data in a sharded and replicated MongoDB backend and runs stateless Node.js instances that can be scaled behind a load balancer.

Key Features

  • First-class IMAP and POP3 support for standard mail clients
  • MongoDB-backed storage for messages and metadata, designed for sharding and replication
  • Stateless architecture for horizontal scaling and high throughput
  • REST API to manage accounts, access, filtering features, and server settings
  • Unicode-first support for internationalized email addresses and folders
  • Built-in account security features such as application-specific passwords, rate limiting, and MFA helpers (TOTP/U2F)
  • Optional support for storing a user GPG public key to encrypt stored emails

Use Cases

  • Hosting IMAP mailboxes for large organizations with many users and large quotas
  • Building an API-driven mail platform where provisioning and operations are automated
  • Running a scalable mail storage and access layer alongside separate SMTP components

Limitations and Considerations

  • Opinionated design may not fit setups that depend on traditional MTA/IMAP stacks and features like Sieve-based workflows
  • Typically used together with additional components (for example, an SMTP server) to form a complete mail system

WildDuck is a strong fit when you need an API-controlled, horizontally scalable IMAP server architecture rather than a classic single-host mail stack. For high-user-count installations, its stateless design and database-backed storage simplify scaling and operations.

2.1kstars
274forks
#9
SOGo

SOGo

Open source groupware suite providing webmail, calendaring, address books, and shared resources via open standards like IMAP, CalDAV, and CardDAV.

SOGo screenshot

SOGo is a fast, scalable groupware (collaboration) server that provides webmail, calendars, and address books through a modern web interface and open protocols. It is designed to sit alongside existing mail infrastructure and give users a unified experience across desktop and mobile clients.

Key Features

  • AJAX-based web interface for mail, calendars, and contacts
  • Standards-based interoperability with existing systems via IMAP, CalDAV, and CardDAV
  • Mobile synchronization support via Microsoft ActiveSync
  • Resource sharing, delegation, and permission handling for calendars and address books
  • Works with many native clients without requiring plugins (depending on client capabilities)

Use Cases

  • Provide a webmail and groupware frontend on top of an existing IMAP mail server
  • Replace proprietary groupware with an open-standards collaboration server for organizations
  • Offer shared calendars/contacts with permission management for teams and communities

Limitations and Considerations

  • Requires integration with external mail services (for example IMAP/SMTP servers) rather than being a complete mail server by itself

SOGo is a strong fit for deployments that prioritize open standards, scalability, and broad client compatibility. It can be used as a central collaboration layer to provide consistent mail, calendar, and contact access across many devices and clients.

2.1kstars
301forks
#10
iRedMail

iRedMail

Automated open-source mail server installer bundling Postfix, Dovecot, webmail, anti-spam/antivirus and LDAP/SQL backends for mainstream Linux/BSD.

iRedMail screenshot

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)

1.7kstars
248forks
#11
Dovecot

Dovecot

High-performance, standards-compliant IMAP/POP3/LMTP server with flexible authentication, extensible plugin system (Lua, Sieve) and OpenSSL TLS support.

Dovecot screenshot

Dovecot is a secure, high-performance IMAP/POP3/LMTP server and mail storage backend designed for reliability, standards compliance and operational scalability. It provides mailbox indexing, flexible authentication backends and a plugin architecture used by large ISPs and hosting providers. (dovecot.org)

Key Features

  • High-performance mailbox indexing with support for Maildir and mbox formats and self-optimizing indexes.
  • Flexible authentication backends with many passdb/userdb options and integration points for MTAs (Postfix, Exim) for SMTP authentication.
  • Standards-compliant IMAP/POP3/LMTP implementation with many protocol workarounds for client interoperability.
  • Extensible plugin system: native Lua scripting support and a rich plugin ecosystem (including the Pigeonhole Sieve/ManageSieve project for Sieve-based filtering).
  • TLS/SSL support via OpenSSL with configurable cipher suites, certificates and TLS settings.
  • Admin-friendly diagnostics, self-healing index behavior and support for clustered filesystems with caveats for some network filesystems.

(dovecot.org)

Use Cases

  • Deploying a production-grade IMAP/POP3/LMTP backend for ISPs, telcos and hosting providers requiring high concurrency and scalability.
  • Building mail delivery workflows with server-side filtering using the Pigeonhole Sieve implementation and ManageSieve management.
  • Integrating authentication and SMTP submission with existing infrastructure (system userdbs, SQL/LDAP backends, or custom Lua-based userdb/passdb).

(pigeonhole.dovecot.org)

Limitations and Considerations

  • Some optional features require additional libraries or build-time options (for example, OpenSSL development headers are required for TLS support when compiling from source). (doc.dovecot.org)
  • Using certain clustered/network filesystems (notably NFS) may require careful configuration or workarounds due to caching semantics; administrators should consult filesystem-specific guidance. (dovecot.org)

Dovecot is a mature, widely used mail backend focused on security, performance and extensibility. Its plugin architecture (Lua, Pigeonhole) and broad authentication options make it suitable for both small deployments and large-scale mail services.

1.2kstars
324forks
#12
tine

tine

Open-source PHP groupware providing CalDAV/CardDAV, ActiveSync, email client, CRM, tasks, file manager and Docker images for on-premise collaboration.

tine screenshot

tine is a modular, PHP-based groupware platform that provides integrated collaboration services for organizations. It bundles calendar, contacts, mail, tasks, CRM, time tracking and file management with sync protocols for common clients.

Key Features

  • Unified groupware stack: calendar, address book, tasks, email client, CRM, project time tracking and file manager
  • Sync protocols: CalDAV, CardDAV, WebDAV and ActiveSync for broad client compatibility
  • Authentication and user management with role/permission support and licensing options
  • Deployable as OCI/Docker images with support for PHP 8.1–8.3, MySQL/MariaDB and Redis backends
  • Modern web UI built with JavaScript and Vue; server-side runs on PHP (php-fpm) behind Nginx or Apache
  • Extensible add-on architecture and administrative tooling for operators

Use Cases

  • Provide on-premises collaboration for small to medium organizations replacing cloud groupware
  • Centralize CRM, email and time tracking for project billing and client management
  • Synchronize calendars and contacts across mobile and desktop clients using CalDAV/CardDAV/ActiveSync

Limitations and Considerations

  • Official community releases restrict free instances to five user accounts without a licence key
  • Production deployments require careful planning for performance, HA and security; operators should be trained
  • Some enterprise features and commercial support are available only via paid packages

tine is suitable for organizations that need a self-hosted, full-featured groupware platform with broad client compatibility and an extensible modular architecture. It is designed for administrators who can manage PHP/MySQL-based deployments and prefer on-premise control.

20stars
3forks
#13
Simple NixOS Mailserver

Simple NixOS Mailserver

Simple NixOS Mailserver provides NixOS modules to deploy a full email server with SMTP/IMAP, spam filtering, DKIM/DMARC/SPF, and TLS automation.

Simple NixOS Mailserver screenshot

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.

#14
Zimbra Collaboration

Zimbra Collaboration

Self-hosted enterprise collaboration suite providing email, webmail, calendaring, contacts, and administration for organizations.

Zimbra Collaboration screenshot

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.

#15
Courier Mail Server (Courier MTA)

Courier Mail Server (Courier MTA)

Courier is an integrated mail server suite providing ESMTP (MTA), IMAP, POP3, webmail, and mailing lists with optional LDAP/MySQL/PostgreSQL-backed virtual accounts.

Courier Mail Server (Courier MTA) screenshot

Courier Mail Server (often referred to as Courier MTA) is an integrated email server suite that combines mail transfer, mail access, and webmail components under a single framework. It supports common Internet mail protocols and can be used as a relay, a final-delivery server for multiple domains, or a mixed setup.

Key Features

  • ESMTP mail transfer agent with DSN, PIPELINING, 8BITMIME, and message submission support
  • Integrated IMAP and POP3 servers (maildir-based mail storage)
  • Integrated webmail (SqWebMail) with basic web-based calendaring and scheduling
  • Virtual mail accounts backed by LDAP, MySQL, or PostgreSQL, as well as system accounts
  • Built-in mail filtering with support for external filters and per-user filtering rules via Maildrop
  • Mailing list manager with automated bounce processing
  • TLS/SSL support for SMTP, IMAP, POP3, and webmail (STARTTLS and certificate validation options)
  • Optional features such as DNS blacklist checks, authenticated SMTP, and rate limiting

Use Cases

  • Running a combined SMTP/IMAP/POP3/webmail stack for a small organization or homelab
  • Hosting multi-domain email with virtual users stored in LDAP or SQL databases
  • Operating an intermediate relay with integrated filtering and policy controls

Limitations and Considerations

  • IMAP/POP3/webmail components are designed primarily for maildir; mbox support is limited
  • Some SMTP features (such as ETRN) are intentionally not supported

Courier is best suited for administrators who want a cohesive mail system with integrated access services and filtering. Its modular components can be enabled or disabled as needed, and several parts are also available as standalone packages for use with other mail systems.

#16
b1gMail

b1gMail

Open-source webmail and groupware offering email, contacts, calendar, cloud drive, tasks, notes and an admin control panel for multi-tenant email services.

b1gMail screenshot

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)

Why choose an open source alternative?

  • Data ownership: Keep your data on your own servers
  • No vendor lock-in: Freedom to switch or modify at any time
  • Cost savings: Reduce or eliminate subscription fees
  • Transparency: Audit the code and know exactly what's running