Courier Mail Server

At a glance

• Editor score
  5.9 / 10
• Pricing
  Free plan
• Best for
  Traditional Linux mail infrastructure
• Free plan
  Yes
• Paid from
  Free
• License model
  Open-source
• Facts checked
  21 Sep 2026

• Where it wins

  • Combines ESMTP, IMAP, POP3, webmail, filtering, and Maildir storage.
  • Supports LDAP, MySQL, and PostgreSQL authentication back ends.
  • Adds mailing lists, calendaring, and distributed mailbox proxying.

• Where it doesn't

  • Verified platform coverage is limited to Linux and self-hosted deployments.
  • Calendaring is basic and web-based rather than a broader collaboration suite.
  • Requires organizations to operate and maintain their own mail infrastructure.

Our verdict on Courier Mail Server

Courier Mail Server is an open-source, self-hosted mail and groupware server for organizations that operate their own email infrastructure. It brings core mail transport and access services together, including ESMTP relay, IMAP, POP3, HTTP webmail through SqWebMail, and Maildir-based mailbox storage. Its audience is primarily administrators and teams maintaining traditional Linux mail systems rather than buyers seeking a hosted service or a broad cloud collaboration platform.

Courier’s breadth is its main strength. Alongside mail delivery and mailbox access, it includes mail filtering and spam rejection, mailing list management, basic web-based calendaring, and an IMAP/POP3 aggregation proxy for distributed mailboxes. That proxy can support mailbox arrangements across multiple servers, while authentication can connect to LDAP, MySQL, or PostgreSQL. The surrounding integration set also includes PAM, OpenSSL, and GnuTLS, giving Linux administrators several established components to fit into an existing infrastructure.

The product’s trade-off is operational focus. Courier is designed for self-hosted Linux deployments, so it suits teams that want control over their mail stack and are prepared to manage the underlying environment. Its feature set covers the traditional mail-server role well, but the calendaring component is basic and the platform scope is narrow. Choose Courier when ESMTP, IMAP, POP3, Maildir, filtering, authentication flexibility, and mailbox aggregation are central requirements. An alternative is a better fit for teams seeking a hosted service, wider platform coverage, or a more extensive collaboration suite.

Your product? Our editors can test Courier Mail Server in depth and publish a review, labelled as paid · from $149/mo →

Courier Mail Server pricing

Courier Mail Server fact sheet

Courier Mail Server integrations

Courier Mail Server lists 6 integrations on its own site.

• LDAP
• MySQL
• PostgreSQL
• PAM
• OpenSSL
• GnuTLS

Alternatives to Courier Mail Server

• Microsoft Exchange OnlineA Microsoft-centric hosted mailbox service with Outlook, archiving, compliance, and migration tools.9.3
• Zimbra CollaborationA broad open-source suite for organizations that need email, collaboration, and deployment control.9.1
• IceWarpA broad hosted email suite with collaboration, migration tools, and self-hosted deployment.9.0

See all Courier Mail Server alternatives →

Featured on iTechGuides

Courier Mail Server is listed in our Mail Server Software directory. Add the badge to your site — it links back to this page.

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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

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Last updated 7 Oct 2026 · How we research and update