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cyrusimap/cyrus-imapd

Cyrus IMAP is a self-hosted mail, contacts and calendar server that serves email over IMAP, JMAP, POP3, CalDAV, CardDAV and WebDAV.

Open-source alternative to:GmailMicrosoft Exchange

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Last commit
yesterday

What is it?

Cyrus IMAP is an email, contacts and calendar server written in C. It is designed to run on sealed servers where ordinary users do not log in to the host; all user access to mail, contacts and calendars goes through protocols such as JMAP, IMAP, POP3, CalDAV, CardDAV and WebDAV.

The mailbox database lives in a filesystem area private to the Cyrus system. This design allows multiple concurrent read/write connections to the same mailbox, and the server supports access control lists on mailboxes and storage quotas on mailbox hierarchies.

The project publishes source tarballs for releases, raw git source for unreleased changes, and packages shipped by major Linux distributions. The current development series is 3.13, and 3.12 is the stable line that continues to receive security and bug fixes.

Key features

  • 01Serves mail, contacts and calendars over JMAP, IMAP, POP3, CalDAV, CardDAV and WebDAV.
  • 02Stores mailboxes in a private database that permits concurrent read/write access.
  • 03Supports access control lists on mailboxes.
  • 04Enforces storage quotas across mailbox hierarchies.
  • 05Available as release tarballs, git source and Linux distribution packages.

Use cases

  • Running a multi-user mail server on a sealed host where users never log in to the OS.
  • Hosting a self-managed email and calendar service that supports standard mail and CalDAV clients.
  • Operating an organization's mail infrastructure with per-mailbox permissions and quotas.

Quick start

  1. 1

    Download the release source tarball from the releases page

  2. 2

    Configure the build

    ./configure
  3. 3

    Compile the project

    make
  4. 4

    Install Cyrus system-wide

    sudo make install

Things to know

  • Not a stable release: 3.13 is under active development and not considered stable.
  • Building from git source requires many extra dependencies, so release tarballs are recommended for most users.
  • Intended to run on sealed servers where normal users cannot log in, so it is aimed at administrators rather than casual use.
  • License is unclear from metadata (NOASSERTION); check the COPYING file before use.

In collections

Self-hosted email servers and newslettersSelf-hosted apps

Topics

#email#imap#caldav#carddav#jmap#mail-server#calendar#self-hosted

FAQ

What is cyrus-imapd?
Cyrus IMAP is a self-hosted mail, contacts and calendar server that serves email over IMAP, JMAP, POP3, CalDAV, CardDAV and WebDAV. Cyrus IMAP is an email, contacts and calendar server written in C. It is designed to run on sealed servers where ordinary users do not log in to the host; all user access to mail, contacts and calendars goes through protocols such as JMAP, IMAP, POP3, CalDAV, CardDAV and WebDAV.
Is cyrus-imapd free to use? What license does it have?
cyrus-imapd is open source under the Other license. Check the license terms before using it in commercial products.
Is cyrus-imapd still maintained?
Actively maintained. The last commit to cyrus-imapd was on Nov 6, 2026.
What can I use cyrus-imapd for?
Running a multi-user mail server on a sealed host where users never log in to the OS. Hosting a self-managed email and calendar service that supports standard mail and CalDAV clients. Operating an organization's mail infrastructure with per-mailbox permissions and quotas.
How do I install cyrus-imapd?
Download the release source tarball from the releases page Configure the build: ./configure Compile the project: make Install Cyrus system-wide: sudo make install
Where can I get cyrus-imapd?
The source code and installation instructions are on GitHub: https://github.com/cyrusimap/cyrus-imapd

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