mox

README

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

See Quickstart below to get started.

Features

• Quick and easy to start/maintain mail server, for your own domain(s).
• SMTP (with extensions) for receiving, submitting and delivering 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).
• Webserver with serving static files and forwarding requests (reverse proxy), so port 443 can also be used to serve websites.
• Prometheus metrics and structured logging for operational insight.
• "localserve" subcommand for running mox locally for email-related testing/developing, including pedantic mode.

Mox is available under the MIT-license and was created by Mechiel Lukkien, mechiel@ueber.net. Mox includes the Public Suffix List by Mozilla, under Mozilla Public License, v2.0.

Download

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 CGO_ENABLED=0 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:

./mox version

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

You can also run mox with docker image r.xmox.nl/mox, with tags like v0.0.1 and v0.0.1-go1.20.1-alpine3.17.2, see https://r.xmox.nl/repo/mox/. See docker-compose.yml in this repository for instructions on starting. You must run docker with host networking, because mox needs to find your actual public IP's and get the remote IPs for incoming connections, not a local/internal NAT IP.

Quickstart

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] (e.g. mail.example.com), login as root, and run:

# Create mox user and homedir (or pick another name or homedir):
useradd -m -d /home/mox mox

cd /home/mox
... compile or download mox to this directory, see above ...

# Generate config files for your address/domain:
./mox quickstart you@example.com

The quickstart creates an account, generates a password and configuration files, prints the DNS records you need to manually create and prints commands to start mox and optionally install mox as a service.

A dedicated machine is highly recommended because modern email requires HTTPS, and mox currently needs it for automatic TLS. You could combine mox with an existing webserver, but it requires more configuration. If you want to serve websites on the same machine, consider using the webserver built into mox. If you want to run an existing webserver on port 443/80, see "mox help quickstart", it'll tell you to run "./mox quickstart -existing-webserver you@example.com".

After starting, you can access the admin web interface on internal IPs.

Future/development

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.

The code is heavily cross-referenced with the RFCs for readability/maintainability.

Roadmap

• Privilege separation, isolating parts of the application to more restricted sandbox (e.g. new unauthenticated connections).
• DANE and DNSSEC.
• Sending DMARC and TLS reports (currently only receiving).
• OAUTH2 support, for single sign on.
• Add special IMAP mailbox ("Queue?") that contains queued but not-yet-delivered messages.
• Sieve for filtering (for now see Rulesets in the account config)
• Calendaring
• IMAP CONDSTORE and QRESYNC extensions
• IMAP THREAD extension
• Using mox as backup MX.
• Old-style internationalization in messages.
• JMAP
• Webmail
• Autoresponder (out of office/vacation)
• HTTP-based API for sending messages and receiving delivery feedback

There are many smaller improvements to make as well, search for "todo" in the code.

Not supported

But perhaps in the future...

• Functioning as SMTP relay
• Forwarding (to an external address)
• POP3
• Delivery to (unix) OS system users
• Mailing list manager
• Support for pluggable delivery mechanisms
• iOS Mail push notifications (with XAPPLEPUSHSERVICE undocumented imap extension and hard to get APNS certificate)

FAQ - Frequently Asked Questions

Why a new mail server implementation?

Mox aims to make "running a mail server" easy and nearly effortless. Excellent quality mail server software exists, but getting a working setup typically requires you configure half a dozen services (SMTP, IMAP, SPF/DKIM/DMARC, spam filtering). That seems to lead to people no longer running their own mail servers, instead switching to one of the few centralized email providers. Email with SMTP is a long-time decentralized messaging protocol. To keep it decentralized, people need to run their own mail server. Mox aims to make that easy.

Where is the documentation?

See all commands and help text at https://pkg.go.dev/github.com/mjl-/mox/, and example config files at https://pkg.go.dev/github.com/mjl-/mox/config/.

You can get the same information by running "mox" without arguments to list its subcommands and usage, and "mox help [subcommand]" for more details.

The example config files are printed by "mox config describe-static" and "mox config describe-dynamic".

Mox is still in early stages, and documentation is still limited. Please create an issue describing what is unclear or confusing, and we'll try to improve the documentation.

How do I import/export email?

Use the import functionality on the accounts web page to import a zip/tgz with maildirs/mbox files, or use the "mox import maildir" or "mox import mbox" subcommands. You could also use your IMAP email client, add your mox account, and copy or move messages from one account to the other.

Similarly, see the export functionality on the accounts web page and the "mox export maildir" and "mox export mbox" subcommands to export email.

How can I help?

Mox needs users and testing in real-life setups! So just give it a try, send and receive emails through it with your favourite email clients, and file an issue if you encounter a problem or would like to see a feature/functionality implemented.

Instead of switching email for your domain over to mox, you could simply configure mox for a subdomain, e.g. [you]@moxtest.[yourdomain].

If you have experience with how the email protocols are used in the wild, e.g. compatibility issues, limitations, anti-spam measures, specification violations, that would be interesting to hear about.

Pull requests for bug fixes and new code are welcome too. If the changes are large, it helps to start a discussion (create a ticket) before doing all the work.

By contributing (e.g. code), you agree your contributions are licensed under the MIT license (like mox), and have the rights to do so.

Where can I discuss mox?

Join #mox on irc.oftc.net, or #mox on the "Gopher slack".

For bug reports, please file an issue at https://github.com/mjl-/mox/issues/new.

How do I change my password?

Regular users (doing IMAP/SMTP with authentication) can change their password at the account page, e.g. http://localhost/. Or you can set a password with "mox setaccountpassword".

The admin can change the password of any account through the admin page, at http://localhost/admin/ by default (leave username empty when logging in).

The account and admin pages are served on localhost on your mail server. To access these from your browser, run ssh -L 8080:localhost:80 you@yourmachine locally and open http://localhost:8080/[...].

The admin password can be changed with "mox setadminpassword".

How do I configure a second mox instance as a backup MX?

Unfortunately, mox does not yet provide an option for that. Mox does spam filtering based on reputation of received messages. It will take a good amount of work to share that information with a backup MX. Without that information, spammers could use a backup MX to get their spam accepted. Until mox has a proper solution, you can simply run a single SMTP server.

How do I stay up to date?

Please set "CheckUpdates: true" in mox.conf. Mox will check for a new version through a DNS TXT request for _updates.xmox.nl once per 24h. Only if a new version is published will the changelog be fetched and delivered to the postmaster mailbox.

The changelog, including latest update instructions, is at https://updates.xmox.nl/changelog.

You can also monitor newly added releases on this repository with the github "watch" feature, or use the github RSS feed for tags (https://github.com/mjl-/mox/tags.atom) or releases (https://github.com/mjl-/mox/releases.atom), or monitor the docker images.

Keep in mind you have a responsibility to keep the internect-connected software you run up to date and secure.

How do I upgrade my mox installation?

We try to make upgrades effortless and you can typically just put a new binary in place and restart. If manual actions are required, the release notes mention them. Check the release notes of all version between your current installation and the release you're upgrading to.

Before upgrading, make a backup of the data directory with mox backup <destdir>. This writes consistent snapshots of the database files, and duplicates message files from the queue and accounts. Using the new mox binary, run mox verifydata <backupdir> (do NOT use the "live" data directory!) for a dry run. If this fails, an upgrade will probably fail too. Important: verifydata with the new mox binary can modify the database files (due to automatic schema upgrades). So make a fresh backup again before the actual upgrade. See the help output of the "backup" and "verifydata" commands for more details.

During backup, message files are hardlinked if possible. Using a destination directory like data/tmp/backup increases the odds hardlinking succeeds: the default systemd service file specifically mounts the data directory, causing attempts to outside it to fail with an error about cross-device linking.

If an upgrade fails and you have to restore (parts) of the data directory, you should run mox verifydata <datadir> (with the original binary) on the restored directory before starting mox again. If problematic files are found, for example queue or account message files that are not in the database, run mox verifydata -fix <datadir> to move away those files. After a restore, you may also want to run mox bumpuidvalidity <account> for each account for which messages in a mailbox changed, to force IMAP clients to synchronize mailbox state.

How secure is mox?

Security is high on the priority list for mox. Mox is young, so don't expect no bugs at all. Mox does have automated tests for some security aspects, e.g. for login, and uses fuzzing. Mox is written in Go, so some classes of bugs such as buffer mishandling do not typically result in privilege escalation. Of course logic bugs will still exist. If you find any security issues, please email them to mechiel@ueber.net.

I'm now running an email server, but how does email work?

Congrats and welcome to the club! Running an email server on the internet comes with some responsibilities so you should understand how it works. See https://explained-from-first-principles.com/email/ for a thorough explanation.

What are the minimum requirements to run mox?

Mox does not need much. Nowadays most machines are larger than mox needs. You can start with a machine with 512MB RAM, any CPU will do. For storage you should account for the size of the email messages (no compression currently), an additional 15% overhead for the meta data, and add some more headroom. Expand as necessary.

Can I see some screenshots?

Yes, see https://www.xmox.nl/screenshots/.

Mox has an "account" web interface where users can view their account and manage their address configuration, such as rules for automatically delivering certain incoming messages to a specific mailbox.

Mox also has an "admin" web interface where the mox instance administrator can make changes, e.g. add/remove/modify domains/accounts/addresses.

Mox does not have a webmail yet, so there are no screenshots of actual email.

Won't the big email providers block my email?

It is a common misconception that it is impossible to run your own email server nowadays. The claim is that the handful big email providers will simply block your email. However, you can run your own email server just fine, and your email will be accepted, provided you are doing it right.

If your email is rejected, it is often because your IP address has a bad email sending reputation. Email servers often use IP blocklists to reject email networks with a bad email sending reputation. These blocklists often work at the level of whole network ranges. So if you try to run an email server from a hosting provider with a bad reputation (which happens if they don't monitor their network or don't act on abuse/spam reports), your IP too will have a bad reputation and other mail servers (both large and small) may reject messages coming from you. During the quickstart, mox checks if your IPs are on a few often-used blocklists. It's typically not a good idea to host an email server on the cheapest or largest cloud providers: They often don't spend the resources necessary for a good reputation, or they simply block all outgoing SMTP traffic. It's better to look for a technically-focused local provider. They too may initially block outgoing SMTP connections on new machines to prevent spam from their networks. But they will either automatically open up outgoing SMTP traffic after a cool down period (e.g. 24 hours), or after you've contacted their support.

After you get past the IP blocklist checks, email servers use many more signals to determine if your email message could be spam and should be rejected. Mox helps you set up a system that doesn't trigger most of the technical signals (e.g. with SPF/DKIM/DMARC). But there are more signals, for example: Sending to a mail server or address for the first time. Sending from a newly registered domain. Sending messages with content that resembles known spam messages.

Should your email be rejected, you will typically get an error message that explains why. In the case of big email providers the error message often has instructions on how to prove to them you are a legimate sender.

Can I use existing TLS certificates/keys?

Yes. The quickstart command creates a config that uses ACME with Let's Encrypt, but you can change the config file to use existing certificate and key files.

You'll see "ACME: letsencrypt" in the "TLS" section of the "public" Listener. Remove or comment out the ACME-line, and add a "KeyCerts" section like in the example config file in https://pkg.go.dev/github.com/mjl-/mox/config#hdr-mox_conf. You can have multiple certificates and keys: The line with the "-" (dash) is the start of a list item. Duplicate that line up to and including the line with KeyFile for each certificate/key you have. Mox makes a TLS config that holds all specified certificates/keys, and uses it for all services for that Listener (including a webserver), choosing the correct certificate for incoming requests.

Keep in mind that for each email domain you host, you will need a certificate for mta-sts.<domain> and autoconfig.<domain>, unless you disable MTA-STS and autoconfig for that domain.

Mox opens the key and certificate files during initial startup, as root (and passes file descriptors to the unprivileged process). No special permissions are needed on the key and certificate files.

Documentation

Overview

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

• Quick and easy to set up with quickstart and automatic TLS with ACME and Let's Encrypt.
• IMAP4 with extensions for accessing email.
• SMTP with SPF, DKIM, DMARC, DNSBL, MTA-STS, TLSRPT for exchanging email.
• Reputation-based and content-based spam filtering.
• Internationalized email.
• Admin web interface.

Commands

mox [-config config/mox.conf] [-pedantic] ...
mox serve
mox quickstart [-existing-webserver] [-hostname host] user@domain [user | uid]
mox stop
mox setaccountpassword address
mox setadminpassword
mox loglevels [level [pkg]]
mox queue list
mox queue kick [-id id] [-todomain domain] [-recipient address] [-transport transport]
mox queue drop [-id id] [-todomain domain] [-recipient address]
mox queue dump id
mox import maildir accountname mailboxname maildir
mox import mbox accountname mailboxname mbox
mox export maildir dst-dir account-path [mailbox]
mox export mbox dst-dir account-path [mailbox]
mox localserve
mox help [command ...]
mox backup dest-dir
mox verifydata data-dir
mox config test
mox config dnscheck domain
mox config dnsrecords domain
mox config describe-domains >domains.conf
mox config describe-static >mox.conf
mox config account add account address
mox config account rm account
mox config address add address account
mox config address rm address
mox config domain add domain account [localpart]
mox config domain rm domain
mox config describe-sendmail >/etc/moxsubmit.conf
mox config printservice >mox.service
mox example [name]
mox checkupdate
mox cid cid
mox clientconfig domain
mox dkim gened25519 >$selector._domainkey.$domain.ed25519key.pkcs8.pem
mox dkim genrsa >$selector._domainkey.$domain.rsakey.pkcs8.pem
mox dkim lookup selector domain
mox dkim txt <$selector._domainkey.$domain.key.pkcs8.pem
mox dkim verify message
mox dkim sign message
mox dmarc lookup domain
mox dmarc parsereportmsg message ...
mox dmarc verify remoteip mailfromaddress helodomain < message
mox dnsbl check zone ip
mox dnsbl checkhealth zone
mox mtasts lookup domain
mox retrain accountname
mox sendmail [-Fname] [ignoredflags] [-t] [<message]
mox spf check domain ip
mox spf lookup domain
mox spf parse txtrecord
mox tlsrpt lookup domain
mox tlsrpt parsereportmsg message ...
mox version

Many commands talk to a running mox instance, through the ctl file in the data directory. Specify the configuration file (that holds the path to the data directory) through the -config flag or MOXCONF environment variable.

mox serve

Start mox, serving SMTP/IMAP/HTTPS.

Incoming email is accepted over SMTP. Email can be retrieved by users using IMAP. HTTP listeners are started for the admin/account web interfaces, and for automated TLS configuration. Missing essential TLS certificates are immediately requested, other TLS certificates are requested on demand.

usage: mox serve

mox quickstart

Quickstart generates configuration files and prints instructions to quickly set up a mox instance.

Quickstart writes configuration files, prints initial admin and account passwords, DNS records you should create. If you run it on Linux it writes a systemd service file and prints commands to enable and start mox as service.

The user or uid is optional, defaults to "mox", and is the user or uid/gid mox will run as after initialization.

Quickstart assumes mox will run on the machine you run quickstart on and uses its host name and public IPs. On many systems the hostname is not a fully qualified domain name, but only the first dns "label", e.g. "mail" in case of "mail.example.org". If so, quickstart does a reverse DNS lookup to find the hostname, and as fallback uses the label plus the domain of the email address you specified. Use flag -hostname to explicitly specify the hostname mox will run on.

Mox is by far easiest to operate if you let it listen on port 443 (HTTPS) and 80 (HTTP). TLS will be fully automatic with ACME with Let's Encrypt.

You can run mox along with an existing webserver, but because of MTA-STS and autoconfig, you'll need to forward HTTPS traffic for two domains to mox. Run "mox quickstart -existing-webserver ..." to generate configuration files and instructions for configuring mox along with an existing webserver.

But please first consider configuring mox on port 443. It can itself serve domains with HTTP/HTTPS, including with automatic TLS with ACME, is easily configured through both configuration files and admin web interface, and can act as a reverse proxy (and static file server for that matter), so you can forward traffic to your existing backend applications. Look for "WebHandlers:" in the output of "mox config describe-domains" and see the output of "mox example webhandlers".

usage: mox quickstart [-existing-webserver] [-hostname host] user@domain [user | uid]
  -existing-webserver
    	use if a webserver is already running, so mox won't listen on port 80 and 443; you'll have to provide tls certificates/keys, and configure the existing webserver as reverse proxy, forwarding requests to mox.
  -hostname string
    	hostname mox will run on, by default the hostname of the machine quickstart runs on; if specified, the IPs for the hostname are configured for the public listener

mox stop

Shut mox down, giving connections maximum 3 seconds to stop before closing them.

While shutting down, new IMAP and SMTP connections will get a status response indicating temporary unavailability. Existing connections will get a 3 second period to finish their transaction and shut down. Under normal circumstances, only IMAP has long-living connections, with the IDLE command to get notified of new mail deliveries.

usage: mox stop

mox setaccountpassword

Set new password an account.

The password is read from stdin. Secrets derived from the password, but not the password itself, are stored in the account database. The stored secrets are for authentication with: scram-sha-256, scram-sha-1, cram-md5, plain text (bcrypt hash).

Any email address configured for the account can be used.

usage: mox setaccountpassword address

mox setadminpassword

Set a new admin password, for the web interface.

The password is read from stdin. Its bcrypt hash is stored in a file named "adminpasswd" in the configuration directory.

usage: mox setadminpassword

mox loglevels

Print the log levels, or set a new default log level, or a level for the given package.

By default, a single log level applies to all logging in mox. But for each "pkg", an overriding log level can be configured. Examples of packages: smtpserver, smtpclient, queue, imapserver, spf, dkim, dmarc, junk, message, etc.

Specify a pkg and an empty level to clear the configured level for a package.

Valid labels: error, info, debug, trace, traceauth, tracedata.

usage: mox loglevels [level [pkg]]

mox queue list

List messages in the delivery queue.

This prints the message with its ID, last and next delivery attempts, last error.

usage: mox queue list

mox queue kick

Schedule matching messages in the queue for immediate delivery.

Messages deliveries are normally attempted with exponential backoff. The first retry after 7.5 minutes, and doubling each time. Kicking messages sets their next scheduled attempt to now, it can cause delivery to fail earlier than without rescheduling.

With the -transport flag, future delivery attempts are done using the specified transport. Transports can be configured in mox.conf, e.g. to submit to a remote queue over SMTP.

usage: mox queue kick [-id id] [-todomain domain] [-recipient address] [-transport transport]
  -id int
    	id of message in queue
  -recipient string
    	recipient email address
  -todomain string
    	destination domain of messages
  -transport string
    	transport to use for the next delivery

mox queue drop

Remove matching messages from the queue.

Dangerous operation, this completely removes the message. If you want to store the message, use "queue dump" before removing.

usage: mox queue drop [-id id] [-todomain domain] [-recipient address]
  -id int
    	id of message in queue
  -recipient string
    	recipient email address
  -todomain string
    	destination domain of messages

mox queue dump

Dump a message from the queue.

The message is printed to stdout and is in standard internet mail format.

usage: mox queue dump id

mox import maildir

Import a maildir into an account.

By default, messages will train the junk filter based on their flags and, if "automatic junk flags" configuration is set, based on mailbox naming.

If the destination mailbox is "Sent", the recipients of the messages are added to the message metadata, causing later incoming messages from these recipients to be accepted, unless other reputation signals prevent that.

Users can also import mailboxes/messages through the account web page by uploading a zip or tgz file with mbox and/or maildirs.

Mailbox flags, like "seen", "answered", will be imported. An optional dovecot-keywords file can specify additional flags, like Forwarded/Junk/NotJunk.

The maildir files/directories are read by the mox process, so make sure it has access to the maildir directories/files.

usage: mox import maildir accountname mailboxname maildir

mox import mbox

Import an mbox into an account.

Using mbox is not recommended, maildir is a better defined format.

By default, messages will train the junk filter based on their flags and, if "automatic junk flags" configuration is set, based on mailbox naming.

If the destination mailbox is "Sent", the recipients of the messages are added to the message metadata, causing later incoming messages from these recipients to be accepted, unless other reputation signals prevent that.

Users can also import mailboxes/messages through the account web page by uploading a zip or tgz file with mbox and/or maildirs.

The mailbox is read by the mox process, so make sure it has access to the maildir directories/files.

usage: mox import mbox accountname mailboxname mbox

mox export maildir

Export one or all mailboxes from an account in maildir format.

Export bypasses a running mox instance. It opens the account mailbox/message database file directly. This may block if a running mox instance also has the database open, e.g. for IMAP connections. To export from a running instance, use the accounts web page.

usage: mox export maildir dst-dir account-path [mailbox]

mox export mbox

Export messages from one or all mailboxes in an account in mbox format.

Using mbox is not recommended. Maildir is a better format.

Export bypasses a running mox instance. It opens the account mailbox/message database file directly. This may block if a running mox instance also has the database open, e.g. for IMAP connections. To export from a running instance, use the accounts web page.

For mbox export, "mboxrd" is used where message lines starting with the magic "From " string are escaped by prepending a >. All ">*From " are escaped, otherwise reconstructing the original could lose a ">".

usage: mox export mbox dst-dir account-path [mailbox]

mox localserve

Start a local SMTP/IMAP server that accepts all messages, useful when testing/developing software that sends email.

Localserve starts mox with a configuration suitable for local email-related software development/testing. It listens for SMTP/Submission(s), IMAP(s) and HTTP(s), on the regular port numbers + 1000.

Data is stored in the system user's configuration directory under "mox-localserve", e.g. $HOME/.config/mox-localserve/ on linux, but can be overridden with the -dir flag. If the directory does not yet exist, it is automatically initialized with configuration files, an account with email address mox@localhost and password moxmoxmox, and a newly generated self-signed TLS certificate.

All incoming email to any address is accepted (if checks pass), unless the recipient localpart ends with:

- "temperror": fail with a temporary error code - "permerror": fail with a permanent error code - [45][0-9][0-9]: fail with the specific error code - "timeout": no response (for an hour)

If the localpart begins with "mailfrom" or "rcptto", the error is returned during those commands instead of during "data".

usage: mox localserve
  -dir string
    	configuration storage directory (default "$userconfigdir/mox-localserve")
  -ip string
    	serve on this ip instead of default 127.0.0.1 and ::1. only used when writing configuration, at first launch.

mox help

Prints help about matching commands.

If multiple commands match, they are listed along with the first line of their help text. If a single command matches, its usage and full help text is printed.

usage: mox help [command ...]

mox backup

Creates a backup of the data directory.

Backup creates consistent snapshots of the databases and message files and copies other files in the data directory. Empty directories are not copied. These files can then be stored elsewhere for long-term storage, or used to fall back to should an upgrade fail. Simply copying files in the data directory while mox is running can result in unusable database files.

Message files never change (they are read-only, though can be removed) and are hardlinked so they don't consume additional space. If hardlinking fails, for example when the backup destination directory is on a different file system, a regular copy is made. Using a destination directory like "data/tmp/backup" increases the odds hardlinking succeeds: the default systemd service file specifically mounts the data directory, causing attempts to hardlink outside it to fail with an error about cross-device linking.

All files in the data directory that aren't recognized (i.e. other than known database files, message files, an acme directory, the "tmp" directory, etc), are stored, but with a warning.

A clean successful backup does not print any output by default. Use the -verbose flag for details, including timing.

To restore a backup, first shut down mox, move away the old data directory and move an earlier backed up directory in its place, run "mox verifydata", possibly with the "-fix" option, and restart mox. After the restore, you may also want to run "mox bumpuidvalidity" for each account for which messages in a mailbox changed, to force IMAP clients to synchronize mailbox state.

Before upgrading, to check if the upgrade will likely succeed, first make a backup, then use the new mox binary to run "mox verifydata" on the backup. This can change the backup files (e.g. upgrade database files, move away unrecognized message files), so you should make a new backup before actually upgrading.

usage: mox backup dest-dir
  -verbose
    	print progress

mox verifydata

Verify the contents of a data directory, typically of a backup.

Verifydata checks all database files to see if they are valid BoltDB/bstore databases. It checks that all messages in the database have a corresponding on-disk message file and there are no unrecognized files. If option -fix is specified, unrecognized message files are moved away. This may be needed after a restore, because messages enqueued or delivered in the future may get those message sequence numbers assigned and writing the message file would fail. Consistency of message/mailbox UID, UIDNEXT and UIDVALIDITY is verified as well.

Because verifydata opens the database files, schema upgrades may automatically be applied. This can happen if you use a new mox release. It is useful to run "mox verifydata" with a new binary before attempting an upgrade, but only on a copy of the database files, as made with "mox backup". Before upgrading, make a new backup again since "mox verifydata" may have upgraded the database files, possibly making them potentially no longer readable by the previous version.

usage: mox verifydata data-dir
  -fix
    	fix fixable problems, such as moving away message files not referenced by their database

mox config test

Parses and validates the configuration files.

If valid, the command exits with status 0. If not valid, all errors encountered are printed.

usage: mox config test

mox config dnscheck

Check the DNS records with the configuration for the domain, and print any errors/warnings.

usage: mox config dnscheck domain

mox config dnsrecords

Prints annotated DNS records as zone file that should be created for the domain.

The zone file can be imported into existing DNS software. You should review the DNS records, especially if your domain previously/currently has email configured.

usage: mox config dnsrecords domain

mox config describe-domains

Prints an annotated empty configuration for use as domains.conf.

The domains configuration file contains the domains and their configuration, and accounts and their configuration. This includes the configured email addresses. The mox admin web interface, and the mox command line interface, can make changes to this file. Mox automatically reloads this file when it changes.

Like the static configuration, the example domains.conf printed by this command needs modifications to make it valid.

usage: mox config describe-domains >domains.conf

mox config describe-static

Prints an annotated empty configuration for use as mox.conf.

The static configuration file cannot be reloaded while mox is running. Mox has to be restarted for changes to the static configuration file to take effect.

This configuration file needs modifications to make it valid. For example, it may contain unfinished list items.

usage: mox config describe-static >mox.conf

mox config account add

Add an account with an email address and reload the configuration.

Email can be delivered to this address/account. A password has to be configured explicitly, see the setaccountpassword command.

usage: mox config account add account address

mox config account rm

Remove an account and reload the configuration.

Email addresses for this account will also be removed, and incoming email for these addresses will be rejected.

usage: mox config account rm account

mox config address add

Adds an address to an account and reloads the configuration.

If address starts with a @ (i.e. a missing localpart), this is a catchall address for the domain.

usage: mox config address add address account

mox config address rm

Remove an address and reload the configuration.

Incoming email for this address will be rejected after removing an address.

usage: mox config address rm address

mox config domain add

Adds a new domain to the configuration and reloads the configuration.

The account is used for the postmaster mailboxes the domain, including as DMARC and TLS reporting. Localpart is the "username" at the domain for this account. If must be set if and only if account does not yet exist.

usage: mox config domain add domain account [localpart]

mox config domain rm

Remove a domain from the configuration and reload the configuration.

This is a dangerous operation. Incoming email delivery for this domain will be rejected.

usage: mox config domain rm domain

mox config describe-sendmail

Describe configuration for mox when invoked as sendmail.

usage: mox config describe-sendmail >/etc/moxsubmit.conf

mox config printservice

Prints a systemd unit service file for mox.

This is the same file as generated using quickstart. If the systemd service file has changed with a newer version of mox, use this command to generate an up to date version.

usage: mox config printservice >mox.service

mox example

List available examples, or print a specific example.

usage: mox example [name]

mox checkupdate

Check if a newer version of mox is available.

A single DNS TXT lookup to _updates.xmox.nl tells if a new version is available. If so, a changelog is fetched from https://updates.xmox.nl, and the individual entries validated with a builtin public key. The changelog is printed.

usage: mox checkupdate

mox cid

Turn an ID from a Received header into a cid, for looking up in logs.

A cid is essentially a connection counter initialized when mox starts. Each log line contains a cid. Received headers added by mox contain a unique ID that can be decrypted to a cid by admin of a mox instance only.

usage: mox cid cid

mox clientconfig

Print the configuration for email clients for a domain.

Sending email is typically not done on the SMTP port 25, but on submission ports 465 (with TLS) and 587 (without initial TLS, but usually added to the connection with STARTTLS). For IMAP, the port with TLS is 993 and without is 143.

Without TLS/STARTTLS, passwords are sent in clear text, which should only be configured over otherwise secured connections, like a VPN.

usage: mox clientconfig domain

mox dkim gened25519

Generate a new ed25519 key for use with DKIM.

Ed25519 keys are much smaller than RSA keys of comparable cryptographic strength. This is convenient because of maximum DNS message sizes. At the time of writing, not many mail servers appear to support ed25519 DKIM keys though, so it is recommended to sign messages with both RSA and ed25519 keys.

usage: mox dkim gened25519 >$selector._domainkey.$domain.ed25519key.pkcs8.pem

mox dkim genrsa

Generate a new 2048 bit RSA private key for use with DKIM.

The generated file is in PEM format, and has a comment it is generated for use with DKIM, by mox.

usage: mox dkim genrsa >$selector._domainkey.$domain.rsakey.pkcs8.pem

mox dkim lookup

Lookup and print the DKIM record for the selector at the domain.

usage: mox dkim lookup selector domain

mox dkim txt

Print a DKIM DNS TXT record with the public key derived from the private key read from stdin.

The DNS should be configured as a TXT record at $selector._domainkey.$domain.

usage: mox dkim txt <$selector._domainkey.$domain.key.pkcs8.pem

mox dkim verify

Verify the DKIM signatures in a message and print the results.

The message is parsed, and the DKIM-Signature headers are validated. Validation of older messages may fail because the DNS records have been removed or changed by now, or because the signature header may have specified an expiration time that was passed.

usage: mox dkim verify message

mox dkim sign

Sign a message, adding DKIM-Signature headers based on the domain in the From header.

The message is parsed, the domain looked up in the configuration files, and DKIM-Signature headers generated. The message is printed with the DKIM-Signature headers prepended.

usage: mox dkim sign message

mox dmarc lookup

Lookup dmarc policy for domain, a DNS TXT record at _dmarc.<domain>, validate and print it.

usage: mox dmarc lookup domain

mox dmarc parsereportmsg

Parse a DMARC report from an email message, and print its extracted details.

DMARC reports are periodically mailed, if requested in the DMARC DNS record of a domain. Reports are sent by mail servers that received messages with our domain in a From header. This may or may not be legatimate email. DMARC reports contain summaries of evaluations of DMARC and DKIM/SPF, which can help understand email deliverability problems.

usage: mox dmarc parsereportmsg message ...

mox dmarc verify

Parse an email message and evaluate it against the DMARC policy of the domain in the From-header.

mailfromaddress and helodomain are used for SPF validation. If both are empty, SPF validation is skipped.

mailfromaddress should be the address used as MAIL FROM in the SMTP session. For DSN messages, that address may be empty. The helo domain was specified at the beginning of the SMTP transaction that delivered the message. These values can be found in message headers.

usage: mox dmarc verify remoteip mailfromaddress helodomain < message

mox dnsbl check

Test if IP is in the DNS blocklist of the zone, e.g. bl.spamcop.net.

If the IP is in the blocklist, an explanation is printed. This is typically a URL with more information.

usage: mox dnsbl check zone ip

mox dnsbl checkhealth

Check the health of the DNS blocklist represented by zone, e.g. bl.spamcop.net.

The health of a DNS blocklist can be checked by querying for 127.0.0.1 and 127.0.0.2. The second must and the first must not be present.

usage: mox dnsbl checkhealth zone

mox mtasts lookup

Lookup the MTASTS record and policy for the domain.

MTA-STS is a mechanism for a domain to specify if it requires TLS connections for delivering email. If a domain has a valid MTA-STS DNS TXT record at _mta-sts.<domain> it signals it implements MTA-STS. A policy can then be fetched at https://mta-sts.<domain>/.well-known/mta-sts.txt. The policy specifies the mode (enforce, testing, none), which MX servers support TLS and should be used, and how long the policy can be cached.

usage: mox mtasts lookup domain

mox retrain

Recreate and retrain the junk filter for the account.

Useful after having made changes to the junk filter configuration, or if the implementation has changed.

usage: mox retrain accountname

mox sendmail

Sendmail is a drop-in replacement for /usr/sbin/sendmail to deliver emails sent by unix processes like cron.

If invoked as "sendmail", it will act as sendmail for sending messages. Its intention is to let processes like cron send emails. Messages are submitted to an actual mail server over SMTP. The destination mail server and credentials are configured in /etc/moxsubmit.conf, see mox config describe-sendmail. The From message header is rewritten to the configured address. When the addressee appears to be a local user, because without @, the message is sent to the configured default address.

If submitting an email fails, it is added to a directory moxsubmit.failures in the user's home directory.

Most flags are ignored to fake compatibility with other sendmail implementations. A single recipient or the -t flag with a To-header is required. With the -t flag, Cc and Bcc headers are not handled specially, so Bcc is not removed and the addresses do not receive the email.

/etc/moxsubmit.conf should be group-readable and not readable by others and this binary should be setgid that group:

groupadd moxsubmit
install -m 2755 -o root -g moxsubmit mox /usr/sbin/sendmail
touch /etc/moxsubmit.conf
chown root:moxsubmit /etc/moxsubmit.conf
chmod 640 /etc/moxsubmit.conf
# edit /etc/moxsubmit.conf

usage: mox sendmail [-Fname] [ignoredflags] [-t] [<message]

mox spf check

Check the status of IP for the policy published in DNS for the domain.

IPs may be allowed to send for a domain, or disallowed, and several shades in between. If not allowed, an explanation may be provided by the policy. If so, the explanation is printed. The SPF mechanism that matched (if any) is also printed.

usage: mox spf check domain ip

mox spf lookup

Lookup the SPF record for the domain and print it.

usage: mox spf lookup domain

mox spf parse

Parse the record as SPF record. If valid, nothing is printed.

usage: mox spf parse txtrecord

mox tlsrpt lookup

Lookup the TLSRPT record for the domain.

A TLSRPT record typically contains an email address where reports about TLS connectivity should be sent. Mail servers attempting delivery to our domain should attempt to use TLS. TLSRPT lets them report how many connection successfully used TLS, and how what kind of errors occurred otherwise.

usage: mox tlsrpt lookup domain

mox tlsrpt parsereportmsg

Parse and print the TLSRPT in the message.

The report is printed in formatted JSON.

usage: mox tlsrpt parsereportmsg message ...

mox version

Prints this mox version.

usage: mox version