Mox is a modern full-featured open source secure mail server for low-maintenance self-hosted email.

See Quickstart below to get started.

Mox features:

• Quick and easy to start/maintain mail server, for your own domain(s).
• SMTP (with extensions) for receiving and submitting email.
• IMAP4 (with extensions) for giving email clients access to email.
• Automatic TLS with ACME, for use with Let’s Encrypt and other CA’s.
• SPF, verifying that a remote host is allowed to sent email for a domain.
• DKIM, verifying that a message is signed by the claimed sender domain,
  and for signing emails sent by mox for others to verify.
• DMARC, for enforcing SPF/DKIM policies set by domains. Incoming DMARC
  aggregate reports are analyzed.
• Reputation tracking, learning (per user) host- and domain-based reputation from
  (Non-)Junk email.
• Bayesian spam filtering that learns (per user) from (Non-)Junk email.
• Slowing down senders with no/low reputation or questionable email content
  (similar to greylisting). Rejected emails are stored in a mailbox called Rejects
  for a short period, helping with misclassified legitimate synchronous
  signup/login/transactional emails.
• Internationalized email, with unicode names in domains and usernames
  (“localparts”).
• TLSRPT, parsing reports about TLS usage and issues.
• MTA-STS, for ensuring TLS is used whenever it is required. Both serving of
  policies, and tracking and applying policies of remote servers.
• Web admin interface that helps you set up your domains and accounts
  (instructions to create DNS records, configure
  SPF/DKIM/DMARC/TLSRPT/MTA-STS), for status information, managing
  accounts/domains, and modifying the configuration file.
• Autodiscovery (with SRV records, Microsoft-style and Thunderbird-style) for
  easy account setup (though not many clients support it).
• Prometheus metrics and structured logging for operational insight.

Not supported (but perhaps in the future):

• Webmail
• HTTP-based API for sending messages and receiving delivery feedback
• Calendaring
• Functioning as SMTP relay
• Forwarding (to an external address)
• Autoresponders
• POP3
• Delivery to (unix) OS system users
• Sieve for filtering
• PGP or S/MIME
• Mailing list manager
• Support for pluggable delivery mechanisms.

Mox has automated tests, including for interoperability with Postfix for SMTP.

Mox is manually tested with email clients: Mozilla Thunderbird, mutt, iOS Mail,
macOS Mail, Android Mail, Microsoft Outlook.

Mox is also manually tested to interoperate with popular cloud providers:
gmail.com, outlook.com, yahoo.com, proton.me.

Mox is implemented in Go, a modern safe programming language, and has a focus on
security.

Mox is available under the MIT-license.
Mox includes the Public Suffix List by Mozilla, under Mozilla Public License, v. 2.0.

Mox was created by Mechiel Lukkien, mechiel@ueber.net.

For discussions/talk, join #mox on irc.oftc.net, or #mox on the “Gopher slack”.

You can easily (cross) compile mox if you have a recent Go toolchain installed
(see “go version”, it must be >= 1.19; otherwise, see https://go.dev/dl/ or
https://go.dev/doc/manage-install and $HOME/go/bin):

GOBIN=$PWD go install github.com/mjl-/mox@latest

Or you can download a binary built with the latest Go toolchain from
https://beta.gobuilds.org/github.com/mjl-/mox, and symlink or rename it to
“mox”.

Verify you have a working mox binary:

Note: Mox only compiles/works on unix systems, not on Plan 9 or Windows.

The easiest way to get started with serving email for your domain is to get a
vm/machine dedicated to serving email, name it [host].[domain], login as an
a