Private and open-source alternatives to Microsoft Exchange Server
12 mail server software rated against the same public privacy criteria as Microsoft Exchange Server (Exchange), with our picks first.
Why look for an alternative?
- Open source: no. Closed source.
- No trackers or telemetry: no. Microsoft websites use third-party cookies and web beacons, including for personalized ads. The server sends diagnostic data to Microsoft through the Emergency Mitigation service unless it is disabled.
- Independent audit: no. No independent audit is published.
See the full Microsoft Exchange Server rating.
The alternatives
Stalwart Grade A
Self-hosted mail and collaboration server written in Rust, with JMAP, IMAP, POP3, SMTP, CalDAV, CardDAV and WebDAV support, built-in spam filtering and a web admin interface.
Based in the United Kingdom (Five Eyes). Stalwart scores 100 out of 100 (grade A) on the mail server software criteria. It meets 4 of 4 criteria: open source, no trackers or telemetry, no ads or data sales and independent audit.
Dovecot Grade A
IMAP and POP3 server for Linux and Unix that stores and serves mailboxes, with support for Sieve filtering through Pigeonhole. The Community Edition is open source.
Based in Finland. Dovecot scores 90 out of 100 (grade A) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
Forward Email Grade B
Self-hosted version of the Forward Email service, installed with a script that deploys Docker containers. It includes MX, SMTP, IMAP, POP3, CalDAV and CardDAV servers, encrypted SQLite mailboxes, a web interface and optional backups to S3-compatible storage.
Based in the United States (Five Eyes). Forward Email scores 85 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no ads or data sales and independent audit.
Docker Mailserver Grade B
Self-hosted mail server in a single Docker container, with SMTP, IMAP, POP3, spam and virus filtering, configured through files and environment variables.
Docker Mailserver scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
iRedMail Grade B
Installer script that sets up a complete mail server on Linux or BSD from open-source components such as Postfix, Dovecot, Roundcube and SpamAssassin.
iRedMail scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
Maddy Grade B
All-in-one mail server written in Go that replaces Postfix, Dovecot and OpenDKIM with a single daemon, handling SMTP, IMAP, DKIM, SPF, DMARC, DANE and MTA-STS.
Maddy scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
Mail-in-a-box Grade B
Self-hosted mail server setup for a single Ubuntu machine, with SMTP, IMAP, webmail, contacts, calendar, spam filtering and backups preconfigured.
Mail-in-a-box scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
mailcow Grade B
Self-hosted mail server suite based on Docker, with SMTP, IMAP, the SOGo webmail and groupware, spam filtering and a web admin interface.
mailcow scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
Mailu Grade B
Self-hosted mail server built from Docker containers, with SMTP, IMAP, webmail, spam and virus filtering and a web admin interface.
Mailu scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
Mox Grade B
Mail server written in Go for low-maintenance self-hosting, combining SMTP, IMAP, webmail, SPF, DKIM, DMARC, MTA-STS, automatic TLS and spam filtering in one program.
Mox scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
Postfix Grade B
Mail transfer agent that routes and delivers email over SMTP, used on many Linux and Unix servers as the default mail server.
Postfix scores 80 out of 100 (grade B) on the mail server software criteria. It meets 3 of 4 criteria: open source, no trackers or telemetry and no ads or data sales.
Modoboa Grade C
Self-hosted mail hosting and management platform built on Postfix and Dovecot, with a web admin interface, webmail, calendars, contacts and spam filtering.
Modoboa scores 65 out of 100 (grade C) on the mail server software criteria. It meets 2 of 4 criteria: open source and no ads or data sales.