Twake Mail

Best Self Hosted Alternatives to Twake Mail

A curated collection of the 18 best self hosted alternatives to Twake Mail.

Hosted business email and calendaring service offering secure, privacy-focused mailboxes with webmail, IMAP/SMTP access, and calendar/contact management for organizations. Part of the Twake collaboration suite emphasizing data sovereignty.

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
Mox

Mox

All-in-one secure mail server with SMTP, IMAP, webmail, automatic TLS (ACME), and built-in SPF/DKIM/DMARC plus junk filtering for low-maintenance domains.

Mox screenshot

Mox is a modern, security-focused, all-in-one email server designed to make running email for your own domain straightforward and low-maintenance. It bundles core mail protocols and deliverability tooling into a single application, with an admin UI and strong operational visibility.

Key Features

  • SMTP server for receiving, submission, and delivery, with modern extensions
  • IMAP4 server (with extensions) for email client access
  • Built-in webmail for reading and sending email in the browser
  • Deliverability features including SPF, DKIM, and DMARC (including aggregate reports)
  • Modern transport security support such as ACME-managed TLS, MTA-STS and DANE, plus TLS reporting
  • Reputation and content-based junk filtering, including per-user Bayesian spam learning and throttling of low-reputation senders
  • Admin web interface for managing domains, accounts, aliases/lists, and configuration guidance (including DNS record instructions)
  • Account autodiscovery support for easier client configuration
  • Optional built-in web server and reverse proxy capabilities
  • HTTP/JSON API and webhooks for transactional email and inbound/delivery events, plus Prometheus metrics and structured logging

Use Cases

  • Hosting email for personal or small-organization domains with a single integrated stack
  • Running a transactional mail endpoint with API-driven sending and delivery event callbacks
  • Email testing and development using the local-only test mode

Limitations and Considerations

  • POP3 is not supported
  • Some advanced features (for example JMAP, Sieve, OAuth2 login, and full mailing list management) are listed as roadmap items rather than fully implemented

Mox is a good fit when you want a cohesive mail server that minimizes external dependencies while still supporting a modern email security and deliverability stack. Its integrated approach, admin UI, and operational tooling aim to reduce the ongoing effort typically associated with running mail infrastructure.

5.4kstars
177forks
#6
Modoboa

Modoboa

Modoboa is an open source mail server management platform with a modern web UI, integrating Postfix and Dovecot with admin tools, webmail, calendar, and address book.

Modoboa screenshot

Modoboa is an open source mail hosting and management platform that helps you deploy and operate a full email server through a modern web interface. It integrates common mail components (MTA/IMAP, filtering, reputation and policy features) around a central SQL database.

Key Features

  • Web-based administration panel for domains, mailboxes, and aliases
  • Integrated webmail with a simplified user interface
  • Calendar and address book features
  • Per-user mail filtering with Sieve and auto-reply messages
  • Reputation and deliverability tooling including DNSBL checks and DMARC reporting
  • Optional integrations for content filtering/quarantine workflows (for example via Amavis)
  • Email traffic statistics and reporting dashboards
  • Modular architecture via extensions for adding functionality

Use Cases

  • Hosting email for a small business or organization with multiple domains and users
  • Replacing third-party email providers while keeping a webmail-based workflow
  • Providing managed mail services with admin and migration tooling

Modoboa is a practical choice for teams that want a unified UI to deploy, configure, and manage a standards-based mail stack while keeping control over data and policies.

3.4kstars
454forks
#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
Sendmail Open Source

Sendmail Open Source

Open Source Sendmail provides a subset of Proofpoint's Sendmail Sentrion MTA for large-scale mail deployments; current release is 8.16.1 with a PGP-signed tarball and OpenDKIM integration.

Sendmail Open Source screenshot

Sendmail Open Source is the open-source subset of Proofpoint's Sendmail Sentrion platform, designed for large and complex mail environments. The current Open Source release is Sendmail 8.16.1, distributed as a tar.gz archive with a PGP signature, and signed by the 2025 signing key. OpenDKIM is referenced as part of the Open Source offering.

Key Features

  • Open Source subset of Sendmail Sentrion for enterprise-scale environments.
  • Release 8.16.1 available on ftp.sendmail.org as a tar.gz archive with a PGP signature; signatures generated with the 2025 signing key.
  • Includes OpenDKIM integration (DKIM) to authenticate messages.
  • Security and licensing guidance, including CERT contact points and PGP signing keys.

Use Cases

  • Deployments in large, complex mail infrastructures needing a durable open-source MTA with long-term manageability (virtualization, consolidation, cloud migration).
  • Environments requiring verifiable, signed open-source builds from ftp.sendmail.org for audits and compliance.
  • Setups needing DKIM-based mail signing and authentication controls.

Limitations and Considerations

  • The Open Source option is a subset of the full Sendmail Sentrion offering; some enterprise features may be unavailable. Consult a specialist to assess fit.

Conclusion

Sendmail Open Source provides an officially supported open-source path for enterprise-style email deployments within the Sendmail Sentrion lineage. It offers a current release (8.16.1) with signed distributions and OpenDKIM support, suited for organizations able to manage an open-source MTA stack.

#15
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.

#16
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.

#17
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)

#18
Dovel

Dovel

Lightweight SMTP server written in Go that receives and sends email via a single JSON config and executable hooks; supports per-user DKIM and TLS.

Dovel screenshot

Dovel is a lightweight SMTP server written in Go that focuses on simplicity and extensibility. It receives and sends email according to a single JSON configuration file and delegates mailbox/storage actions to user-provided hooks. (pkg.go.dev)

Key Features

  • Written in Go with a single config file (defaults to $XDG_CONFIG_DIR/dovel/config.json) for easy setup and portability.
  • Receives mail and executes executable hooks named receive-<DOMAIN>, passing the message in mbox format to the hook for custom storage or processing.
  • Sends mail using a configured vault/users JSON file and supports per-user DKIM signing for outbound messages.
  • TLS support via certificate and private key fields in the config (used for encrypted SMTP on submission ports).
  • Listens on standard SMTP ports (25, 587, 465, 2525 configurable) and exposes a simple optional web interface for browsing messages.
  • Debug/logging controlled by the DEBUG environment variable for developer troubleshooting. (pkg.go.dev)

Use Cases

  • Self-hosted personal or small-team mail handling where incoming messages are processed by custom scripts (hooks) and stored in custom formats.
  • Developer workflows that need programmatic delivery of inbound email to local tools, APIs, or archiving scripts.
  • Simple transactional mail sender for services that can provide per-user DKIM keys and manage DNS records for deliverability. (pkg.go.dev)

Limitations and Considerations

  • No built-in IMAP/POP3 mailbox server functionality; message storage/management is delegated to hooks so external tooling is needed for mailbox access.
  • No integrated spam filtering, antivirus, or advanced MTA features (bouncing policies, rate limiting, reputational services) — these must be provided externally.
  • Deliverability requires correct DNS/SPF/DKIM/DMARC configuration and operational handling (outbound reputation, PTR records) which are not automated by the server. (pkg.go.dev)

Dovel provides a compact, script-extensible SMTP server implementation intended for users who prefer a minimal, Go-based mail gateway that hands message storage and processing to custom hooks. It is most appropriate where straightforward SMTP receive/send behavior and per-message scripting are sufficient.

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