msmtp ¶

2.1 General commands ¶

‘defaults’ ¶

Set defaults. The following commands will set default values for all following account definitions in the current configuration file.

‘account name [: account[,…]]’ ¶

Start a new account definition with the given name. The current default values are filled in (see defaults).
If a colon and a list of previously defined accounts is given after the account name, the new account, with the filled in default values, will inherit all settings from the accounts in the list.

‘eval [cmd]’ ¶

Replace the current configuration file line with the first line of the output (stdout) of the command cmd. This can be used to decrypt settings or to create them via scripts. For example, eval echo host localhost replaces the current line with host localhost.
Note that every ‘eval’ line will be evaluated when the configuration file is read.
The cmd command must not mess with standard input; if in doubt, append < /dev/null.
Note that for passwords you can also use the passwordeval command instead of eval password cmd. This has the advantage that the command is only evaluated if needed.

‘host hostname’ ¶

The SMTP server to send the mail to. The argument may be a host name or a network address. Every account definition must contain this command.

‘port number’ ¶

The port that the SMTP server listens on. The default is 25 ("smtp"), unless TLS without STARTTLS is used, in which case it is 465 ("smtps").

‘source_ip [IP]’ ¶

Set a source IP address to bind the outgoing connection to. Useful only in special cases on multi-home systems. An empty argument disables this.

‘proxy_host [IP|hostname]’ ¶

Use a SOCKS proxy. All network traffic will go through this proxy host, including DNS queries, except for a DNS query that might be necessary to resolve the proxy host name itself (this can be avoided by using an IP address as proxy host name). An empty argument disables proxy usage. The supported SOCKS protocol version is 5. If you plan to use this with Tor, see also Using msmtp with Tor.

‘proxy_port [number]’ ¶

Set the port number for the proxy host. An empty ‘number’ argument resets this to the default port, which is 1080 ("socks").

‘socket [socketname]’ ¶

Set the file name of a unix domain socket to connect to. This overrides both ‘host’/‘port’ and ‘proxy_host’/‘proxy_port’.

‘timeout (off|seconds)’ ¶

Set or unset a network timeout, in seconds. The argument ‘off’ means that no timeout will be set, which means that the operating system default will be used.

‘protocol (smtp|lmtp)’ ¶

Set the protocol to use. Currently only SMTP and LMTP are supported. SMTP is the default. See port for default ports.

‘domain argument’ ¶

This command sets the argument of the SMTP EHLO (or LMTP LHLO) command, and the domain part of Message-ID headers if msmtp generates them (see set_msgid_header).
The default value ‘localhost’ is stupid but usually works for EHLO. However it does not make sense for Message-ID headers. See set_msgid_header for details.
Possible choices are the domain part of your mail address (provider.example for joe@provider.example) or the fully qualified domain name of your host (if available).
The following substitution patterns are supported:

• %H will be replaced by $HOSTNAME, or if that fails by the host name of the system.
• %C will be replaced by the canonical name of %H.
• %M will be replaced by the contents of /etc/mailname (potentially a different directory is used depending on the build configuration; see the output of ‘msmtp --version’ and look for the location of the system configuration file).

2.2 Authentication commands ¶

See Authentication.

‘auth [(on|off|method)]’ ¶

Enable or disable authentication and optionally choose a method to use. The argument ‘on’ chooses a method automatically. Accepted methods are ‘scram-sha-256-plus’, ‘scram-sha-1-plus’, ‘scram-sha-256’, ‘scram-sha-1’, ‘plain’, ‘gssapi’, ‘external’, ‘oauthbearer’, ‘cram-md5’, ‘digest-md5’, ‘login’, ‘ntlm’, and ‘xoauth2’. See Authentication.

‘user [username]’ ¶

Set the user name for authentication. An empty argument unsets the user name. Authentication must be activated with the ‘auth’ command.

‘password [secret]’ ¶

Set the password for authentication. An empty argument unsets the password. Consider using the ‘passwordeval’ command or a key ring instead of this command, to avoid storing cleartext passwords in the configuration file. See Authentication.

‘passwordeval [cmd]’ ¶

Set the password for authentication to the output (stdout) of the command cmd. This can be used e.g. to decrypt password files on the fly or to query key rings, and thus to avoid storing cleartext passwords.
The cmd command must not mess with standard input; if in doubt, append < /dev/null.
See Authentication.

‘ntlmdomain [ntlmdomain]’ ¶

Set a domain for the ‘ntlm’ authentication method. This is obsolete.

2.3 TLS commands ¶

See Transport Layer Security.

‘tls [(on|off)]’ ¶

Enable or disable TLS (also known as SSL) for secured connections.

‘tls_starttls [(on|off)]’ ¶

Choose the TLS variant: start TLS from within the session (‘on’, default), or tunnel the session through TLS (‘off’).

‘tls_trust_file [file]’ ¶

Activate server certificate verification using a list of trusted Certification Authorities (CAs). The default is the special value ‘system’, which selects the system default. An empty argument disables trust in CAs. If you select a file, it must be in PEM format, and you should also use ‘tls_crl_file’.

‘tls_crl_file [file]’ ¶

Deprecated. This sets a certificate revocation list (CRL) file for TLS, to check for revoked certificates (an empty argument, which is the default, disables this). Nowadays automatic OCSP checks replace CRL file checks.

‘tls_fingerprint [fingerprint]’ ¶

Set the fingerprint of a single certificate to accept for TLS. This certificate will be trusted regardless of its contents (this overrides ‘tls_trust_file’). The fingerprint should be of type SHA256, but can for backwards compatibility also be of type SHA1 or MD5 (please avoid this). The format should be 01:23:45:67:…. Use ‘--serverinfo --tls --tls-certcheck=off --tls-fingerprint=’ to get the server certificate fingerprint.

‘tls_key_file [file]’ ¶

Send a client certificate to the server (use this together with ‘tls_cert_file’). The file must contain the private key of a certificate in PEM format. An empty argument disables this feature.

‘tls_cert_file [file]’ ¶

Send a client certificate to the server (use this together with ‘tls_key_file’). The file must contain a certificate in PEM format. An empty argument disables this feature.

‘tls_certcheck [(on|off)]’ ¶

Enable or disable checks of the server certificate. They are enabled by default.
Disabling them will override ‘tls_trust_file’ and ‘tls_fingerprint’. WARNING: When the checks are disabled, TLS sessions will not be secure!

‘tls_priorities [priorities]’ ¶

Set priorities for TLS session parameters. The default is set by the TLS library and can be selected by using an empty argument to this command. The interpretation of the priorities string depends on the TLS library. Use ‘--version’ to find out which TLS library you use.
For GnuTLS, see the section on Priority Strings in the manual.
For libtls, the priorites string is a space-separated list of parameter strings prefixed with either PROTOCOLS=, CIPHERS=, or ECDHECURVES=. These parameter strings will be passed to the functions ‘tls_config_parse_protocols’, ‘tls_config_set_ciphers’, and ‘tls_config_set_ecdhecurves’. Unrecognized parts of the priorities string will be ignored. Example: PROTOCOLS=TLSv1.3 CIPHERS=ECDHE-RSA-AES128-SHA256 ECDHECURVES=P-384.

‘tls_host_override [host]’ ¶

By default, TLS host verification uses the host name given by the ‘host’ command. This command allows one to use a different host name for verification. This is only useful in special cases.

‘tls_min_dh_prime_bits [bits]’ ¶

Deprecated, use ‘tls_priorities’ instead. Set or unset the minimum number of Diffie-Hellman (DH) prime bits accepted for TLS sessions. The default is set by the TLS library and can be selected by using an empty argument to this command. Only lower the default (for example to 512 bits) if there is no other way to make TLS work with the remote server.

2.4 Commands specific to sendmail mode ¶

See Sendmail mode.

‘from [address]’ ¶

Set the envelope-from address. The following substitution patterns are supported:

• %U will be replaced by $USER, or if that fails by $LOGNAME, or if that fails by the login name of the user running msmtp.
• %H will be replaced by $HOSTNAME, or if that fails by the host name of the system.
• %C will be replaced by the canonical name of %H.
• %M will be replaced by the contents of /etc/mailname (potentially a different directory is used depending on the build configuration; see the output of ‘msmtp --version’ and look for the location of the system configuration file).

Note that the obsolete ‘auto_from’ command replaces this envelope-from address.
To enforce the use of this envelope-from address and ignore the ‘-f’ / ‘--from’ option, see allow_from_override.
See Envelope-from address.
Furthermore, the envelope-from address may be a wildcard pattern as used for file name matching in the shell. This is the case if it contains one of the characters ?, * or [. This allows a variety of envelope-from addresses given with the ‘--from’ option to match a single account.

‘from_full_name name’ ¶

Set a full name to be used in a From header if msmtp adds one. See set_from_header.

‘allow_from_override (on|off)’

By default, the --from option overrides the from command. Set to ‘off’ to disable this.

‘dsn_notify (off|condition)’ ¶

Set the condition(s) under which the mail system should send DSN (Delivery Status Notification) messages. The argument ‘off’ disables explicit DSN requests, which means the mail system decides when to send DSN messages. This is the default. The condition must be ‘never’, to never request notification, or a comma separated list (no spaces!) of one or more of the following: ‘failure’, to request notification on transmission failure, ‘delay’, to be notified of message delays, ‘success’, to be notified of successful transmission. The SMTP server must support the DSN extension. See Delivery Status Notifications.

‘dsn_return (off|amount)’ ¶

This command controls how much of a mail should be returned in DSN (Delivery Status Notification) messages. The argument ‘off’ disables explicit DSN requests, which means the mail system decides how much of a mail it returns in DSN messages. This is the default. The amount must be ‘headers’, to just return the message headers, or ‘full’, to return the full mail. The SMTP server must support the DSN extension. See Delivery Status Notifications.

‘set_from_header [(auto|on|off)]’ ¶

When to set a From header: ‘auto’ adds a From header if the mail does not have one (this is the default), ‘on\’ always sets a From header and overrides any existing one, and ‘off’ never sets a From header.
If the mail server rejects the mail because its From header does not match the envelope from address (a common anti-spam measure), then you might want to set this option to ‘on’.
The From header is created based on the envelope-from address. Disable allow_from_override to prevent programs from setting their own envelope-from address.
For compatibility with older versions, ‘add_missing_from_header [(on|off)]’ is still supported and corresponds to the ‘auto’ and ‘off’ settings.
See Header handling.

‘set_date_header [(auto|off)]’ ¶

When to set a Date header: ‘auto’ adds a Date header if the mail does not have one (this is the default), and ‘off’ never sets a Date header.
For compatibility with older versions, ‘add_missing_date_header [(on|off)]’ is still supported and corresponds to the ‘auto’ and ‘off’ settings.
See Header handling.

‘set_msgid_header [(auto|off)]’ ¶

When to set a Message-ID header: ‘auto’ adds a Message-ID header if the mail does not have one (this is the default), and ‘off’ never sets a Message-ID header.
Message-IDs have the form ‘hash@domain’, where ‘hash’ is a hash over some values that uniquely identify the mail, and ‘domain’ is either the value of the domain command (unless that is the default value ‘localhost’), or the domain part of the envelope-from address (if available), or the host name of the SMTP server. See Header handling.

‘remove_bcc_headers [(on|off)]’ ¶

This command controls whether to remove Bcc headers. The default is to remove them.

‘undisclosed_recipients [(on|off)]’ ¶

When set, the original To, Cc, and Bcc headers of the mail are removed and a single new header line "To: undisclosed-recipients:;" is added. The default setting is off. See Header handling.

‘logfile [file]’ ¶

Enable logging to the specified file. An empty argument disables logging. The file name ‘-’ directs the log information to standard output. See Logging.

‘logfile_time_format [fmt]’ ¶

Set or unset the log file time format. This will be used as the format string for the strftime() function. An empty argument chooses the default (‘"%b %d %H:%M:%S"’). See Logging.

‘syslog [(on|off|facility)]’ ¶

Enable or disable syslog logging. The facility can be one of ‘LOG_USER’, ‘LOG_MAIL’, ‘LOG_LOCAL0’, …, ‘LOG_LOCAL7’. The default is ‘LOG_USER’. Syslog logging is disabled by default. See Logging.

‘aliases [file]’ ¶

Replace local recipients with addresses in the aliases file. The aliases file is a cleartext file containing mappings between a local address and a list of replacement addresses. The mappings are of the form:

local: someone@example.com, person@domain.example

Multiple replacement addresses are separated with commas. Comments start with ’#’ and continue to the end of the line.
The local address ‘default’ has special significance and is matched if the local address is not found in the aliases file. If no ‘default’ alias is found, then the local address is left as is.
Note that alias expansion only affects the mail envelope. The To and Cc headers are not modified.
An empty argument to the aliases command disables the replacement of local addresses. This is the default.

‘auto_from [(on|off)]’ ¶

Obsolete; you can achieve the same and more using the substitution patterns of the ‘from’ command.
Enable or disable automatic envelope-from addresses. The default is ‘off’. When enabled, an envelope-from address of the form user@domain will be generated. The local part will be set to USER or, if that fails, to LOGNAME or, if that fails, to the login name of the current user. The domain part can be set with the ‘maildomain’ command; if that is empty, the address not have a domain part. See Envelope-from address.

‘maildomain [domain]’ ¶

Obsolete; you can achieve the same and more using the substitution patterns of the ‘from’ command.
Set a domain part for the generation of an envelope-from address. See auto_from.

3.1 Synopsis ¶

• Sendmail mode (default):
  msmtp [option…] [--] recipient…
msmtp [option…] -t [--] [recipient…]
• Configuration mode:
  msmtp --configure mailaddress
  
• Server information mode:
  msmtp [option…] --serverinfo
• Remote Message Queue Starting mode:
  msmtp [option…] --rmqs=(host|@domain|#queue)

3.2 Options ¶

Options override configuration file settings. They are compatible with sendmail where appropriate.

• General options
• Changing the mode of operation
• Configuration options
• Options specific to sendmail mode

3.3 Choosing an account ¶

There are three ways to choose the account to use.

1. --account=account
   Use the given account. Command line settings override configuration file settings.
2. --host=hostname
   Use only the settings from the command line; do not use any configuration file data.
3. --from=address or --read-envelope-from
   Choose the first account from the system or user configuration file that has a matching envelope-from address as specified by a from command. This works only when neither --account nor --host is used.
   Subadresses are supported. For example, the envelope from address user+detail@example.com will match the account for user@example.com.
   Furthermore, the envelope-from address of the account may be a wildcard pattern. See from.

If none of the above options is used (or if no account has a matching from command), then the account "default" is used.

3.4 Exit code ¶

The standard exit codes from sysexits.h are used.

3.5 Files ¶

‘SYSCONFDIR/msmtprc’

The system configuration file. Use the --version option to find out what SYSCONFDIR is on your platform.

‘~/.msmtprc or $XDG_CONFIG_HOME/msmtp/config.’

The default user configuration file.

‘~/.netrc and SYSCONFDIR/netrc’

The netrc file contains login information. Before prompting for a password, msmtp will search it in ~/.netrc and SYSCONFDIR/netrc.

3.6 Environment ¶

‘USER, LOGNAME’

These variables override the user’s login name when constructing an envelope-from address. LOGNAME is only used if USER is unset.

‘TMPDIR’

Directory to create temporary files in. If this is unset, a system specific default directory is used. A temporary file is used to buffer the headers of the mail but not the mail body, so the file will not get very large.

‘EMAIL, SMTPSERVER’

These environment variables are used only if neither --host nor --account is used and there is no default account defined in the configuration files. In this case, the host name is taken from SMTPSERVER, and the envelope from address is taken from EMAIL, unless overridden by --from or --read-envelope-from. Currently SMTPSERVER must contain a plain host name (no URL), and EMAIL must contain a plain address (no names or additional information).

4.1 Client Certificates ¶

TLS also allows the server to verify the identity of the client. For this purpose, the client has to present a certificate issued by a CA that the server trusts. To present that certificate, the client also needs the matching key file. You can set the certificate and key files using tls_cert_file and tls_key_file. This mechanism can also be used to authenticate users, so that traditional user / password authentication is not necessary anymore. See the EXTERNAL mechanism in Authentication.

# Enable TLS
tls on
# Enable TLS client certificates
tls_cert_file /path/to/client_cert
tls_key_file /path/to/client_key
# Enable authentication via the EXTERNAL mechanism (optional; depends on server)
# The user name is empty because the server should get it from the client cert
auth external
user ""

You can also use client certificates stored on some external authentication device by specifying GnuTLS device URIs in tls_cert_file and tls_key_file. You can find the correct URIs using p11tool --list-privkeys --login (p11tool is bundled with GnuTLS). If your device requires a PIN to access the data, you can specify that using one of the password mechanisms (e.g. passwordeval, password).

tls_cert_file pkcs11:model=PKCS%2315%20emulated;manufacturer=piv_II;serial=00000000;token=PIV_II%20%28PIV%20Card%20Holder%20pin%29;id=%01;object=Certificate%20for%20PIV%20Authentication;type=cert
tls_key_file  pkcs11:model=PKCS%2315%20emulated;manufacturer=piv_II;serial=00000000;token=PIV_II%20%28PIV%20Card%20Holder%20pin%29;id=%01;object=PIV%20AUTH%20key;type=private
passwordeval  gpg2 --no-tty -q -d ~/.smart-card-pin.gpg

7.1 Envelope-from address ¶

The SMTP server expects a sender mail address for each mail. This is the envelope-from address. It is independent of the From header (because it is part of the mail envelope, not of the mail itself), but in most cases both addresses are the same.

Envelope-from addresses are set with the from command or --from option. The latter can be disabled with the allow_from_override command.

7.2 Logging ¶

When logging is enabled, msmtp will generate one log line for each mail it tries to send.

The line will include the following information:

• Host name of the SMTP server: host=hostname
• Whether TLS was used: tls=(on|off)
• Whether authentication was used: auth=(on|off)
• The user name used for authentication (only if authentication is used): user=name
• The envelope-from address: from=address
• The recipient addresses: recipients=addr1,addr2,…
• The size of the mail as transferred to the server, in bytes (only if the delivery succeeded): mailsize=number
• The SMTP status code and SMTP error message (only in case of failure and only if available): smtpstatus=number, smtpmsg='message'. Multiline SMTP messages will be concatenated into one line.
• The msmtp error message (only in case of failure and only if available): errormsg='message'
• The msmtp exit code (from sysexits.h; ‘EX_OK’ indicates success): exitcode=EX_…

If a logfile is given with the logfile command, this log line will be prepended with the current date and time (formatted according to logfile_time_format) and appended to the specified file.

If syslog logging is enabled with the syslog command, the log line is passed to the syslog service with the specified facility.

7.3 Header handling ¶

Msmtp transmits mails unaltered to the SMTP server, with the following exceptions:

• The Bcc header(s) will be removed. This behavior can be changed with the remove_bcc_headers command,
• A From header will be added if the mail does not have one. This can be changed with the set_from_header command. The header will use the envelope from address and optionally a full name set with the ‘-F’ option.
• A Date header will be added if the mail does not have one. This can be changed with the set_date_header command.
• A Message-ID header will be added if the mail does not have one. This can be changed with the set_msgid_header command.
• When undisclosed_recipients is set, the original To, Cc, and Bcc headers are removed and replaced with "To: undisclosed-recipients:;".

10.1 A user configuration file ¶

# Example for a user configuration file ~/.msmtprc
#
# This file focusses on TLS and authentication. Features not used here include
# logging, timeouts, SOCKS proxies, TLS parameters, Delivery Status Notification
# (DSN) settings, and more.


# Set default values for all following accounts.
defaults

# Use the mail submission port 587 instead of the SMTP port 25.
port 587

# Always use TLS.
tls on

# Set a list of trusted CAs for TLS. The default is to use system settings, but
# you can select your own file.
#tls_trust_file /etc/ssl/certs/ca-certificates.crt


# A freemail service
account freemail

# Host name of the SMTP server
host smtp.freemail.example

# As an alternative to tls_trust_file, you can use tls_fingerprint
# to pin a single certificate. You have to update the fingerprint when the
# server certificate changes, but an attacker cannot trick you into accepting
# a fraudulent certificate. Get the fingerprint with
# $ msmtp --serverinfo --tls --tls-certcheck=off --host=smtp.freemail.example
#tls_fingerprint 00:11:22:33:44:55:66:77:88:99:AA:BB:CC:DD:EE:FF:00:11:22:33

# Envelope-from address
from joe_smith@freemail.example

# Authentication. The password is given using one of five methods, see below.
auth on
user joe.smith

# Password method 1: Add the password to the system keyring, and let msmtp get
# it automatically. To set the keyring password using Gnome's libsecret:
# $ secret-tool store --label=msmtp \
#   host smtp.freemail.example \
#   service smtp \
#   user joe.smith

# Password method 2: Store the password in an encrypted file, and tell msmtp
# which command to use to decrypt it. This is usually used with GnuPG, as in
# this example. Usually gpg-agent will ask once for the decryption password.
passwordeval gpg2 --no-tty -q -d ~/.msmtp-password.gpg

# Password method 3: Store the password directly in this file. Usually it is not
# a good idea to store passwords in cleartext files. If you do it anyway, at
# least make sure that this file can only be read by yourself.
#password secret123

# Password method 4: Store the password in ~/.netrc. This method is probably not
# relevant anymore.

# Password method 5: Do not specify a password. Msmtp will then prompt you for
# it. This means you need to be able to type into a terminal when msmtp runs.


# A second mail address at the same freemail service
account freemail2 : freemail
from joey@freemail.example


# The SMTP server of your ISP
account isp
host mail.isp.example
from smithjoe@isp.example
auth on
user 12345


# Set a default account
account default : freemail

10.2 A system wide configuration file ¶

# A system wide configuration file is optional.
# If it exists, it usually defines a default account.
# This allows msmtp to be used like /usr/sbin/sendmail.
account default

# The SMTP smarthost
host mail.oursite.example

# Use TLS on port 465
port 465
tls on
tls_starttls off

# Construct envelope-from addresses of the form "user@oursite.example"
from %U@oursite.example

# Syslog logging with facility LOG_MAIL instead of the default LOG_USER
syslog LOG_MAIL

10.3 Using msmtp with Mutt ¶

Create a configuration file for msmtp and add the following lines to your Mutt configuration file:

set sendmail="/path/to/msmtp"
set use_from=yes
set realname="Your Name"
set from=you@example.com
set envelope_from=yes

The ‘envelope_from=yes’ option lets Mutt use the -f option of msmtp. Therefore msmtp chooses the first account that matches the from address you@example.com. Alternatively, you can use the -a option:

set sendmail="/path/to/msmtp -a my_account"

Or set everything from the command line:

set sendmail="/path/to/msmtp --host=mailhub -f me@example.com --tls"

See Choosing an account.

If you have multiple mail accounts in your msmtp configuration file and let Mutt use the -f option to choose one, you can easily switch accounts in Mutt with the following Mutt configuration lines:

macro generic "<esc>1" ":set from=you@example.com"
macro generic "<esc>2" ":set from=you@your-employer.example"
macro generic "<esc>3" ":set from=you@some-other-provider.example"

Now you can use <esc>1, <esc>2, and <esc>3 to switch accounts.

The following example uses a different approach: it maps the single key <tab> in Compose context for switching between the various account in a handy visual way. In the same Compose context, = is mapped in order to show the current msmtp account. This example was contributed by Thomas Baruchel.

# Define <tab> and = in order to switch or see the current msmtp account
# Don't forget to put the right path for msmtp binary
macro compose \Cx_ ":set sendmail"
macro compose \Cx| "\Cx_ = \"/usr/local/bin/msmtp"
macro compose \Cx& ":macro compose \\t \\Cx"
macro compose <tab> "\Cx0"
macro compose = "\Cx_\n"
# Put the account in the following lines (here three accounts)
# Don't forget to put the number of the account at the beginning
# of the line, and the number of the next account after the '&'
macro compose \Cx0 "\Cx|\"\n\Cx&1\n\Cx_\n" # default and switch to 1
macro compose \Cx1 "\Cx| -a example_account\"\n\Cx&2\n\Cx_\n" # switch to 2
macro compose \Cx2 "\Cx| -a gmail\"\n\Cx&0\n\Cx_\n" # switch to 0
# End of the accounts

10.4 Using msmtp with mail ¶

Define a default account, and put the following into ~/.mailrc:

set sendmail="/path/to/msmtp"

You need to define a default account, because mail does not allow extra options to the msmtp command line.

10.5 Using msmtp with Tor ¶

Use the following settings:

proxy_host 127.0.0.1
proxy_port 9050
tls on

Use an IP address as proxy host name, so that msmtp does not leak a DNS query when resolving it.
TLS is required to prevent exit hosts from reading your SMTP session. You also need tls_trust_file or tls_fingerprint to check the server identity. Do not set ‘domain’ to something that you do not want to reveal (do not set it at all if possible).

10.6 Aliases file ¶

# Example aliases file

# Send root to Joe and Jane
root: joe_smith@example.com, jane_chang@example.com

# Send cron to Mark
cron: mark_jones@example.com

# Send everything else to admin
default: admin@domain.example

11.1 Example: using msmtpd as a system service ¶

Only use a local interface to listen on. Run msmtpd with correct user rights and permissions (e.g. use ‘CAP_NET_BIND_SERVICE’ to bind to port 25 instead of running as root, or use systemd with inetd service capabilities). Be aware that the pipe command will be run as the same user that msmtpd runs as. Enable logging to syslog with ‘--log=syslog’.

Example for managing msmtpd with ‘start-stop-daemon’:

# start msmtpd
start-stop-daemon --start --pidfile /var/run/msmtpd.pid --make-pidfile --chuid msmtpd --background --exec /usr/local/bin/msmtpd -- --command '/usr/local/bin/msmtp -f %F --'
# stop msmtpd
start-stop-daemon --stop  --pidfile /var/run/msmtpd.pid --remove-pidfile --quiet --signal TERM

11.2 Example: using msmtpd to handle outgoing mail for an SMTP-based mail client ¶

Some mail clients cannot send outgoing mail with a program like msmtp and instead insist on using an SMTP server. You can configure msmtpd to be that SMTP server and hand your outgoing mail over to msmtp.

(Similarly, some mail clients cannot get incoming mail from a local mailbox and insist on using a POP3 or IMAP server. You can configure mpopd to be that POP3 server and serve incoming mail from a local mailbox. See the corresponding section in the mpop manual.)

For this purpose, msmtpd should listen on an unprivileged port, e.g. 2500. Furthermore, msmtpd should require authentication because otherwise anyone connecting to it can send mail using your account, even if it’s just other users or processes on your local machine.

Let’s use the user name msmtpd-user for this purpose. You have two options to manage the password:

1. Store the password in your key ring, e.g. with

   secret-tool store --label=msmtpd host localhost service smtp user msmtpd-user
   

   In this case, use the msmtpd option ‘--auth=msmtpd-user’.

2. Store the password in an encrypted file and use the passwordeval mechanism. Example for gpg:

   msmtpd ... --auth=msmtpd-user,'gpg -q -d ~/.msmtpd-password.gpg'
   

The complete command then is (using the keyring):

msmtpd --port=2500 --auth=msmtpd-user --command='/path/to/your/msmtp -f %F --'

The mail client software must then be configured to use ‘localhost’ at port ‘2500’ for outgoing mail via SMTP, and to use authentication with user ‘msmtpd-user’ and the password you chose. The mail client will probably complain that the SMTP server does not support TLS, but in this special case that is ok since all communication between your mail client and msmtpd will stay on the local machine.

This setup also works with multiple mail accounts. Msmtp will pick the correct one based on the envelope-from address given to it via ‘-f %F’. You do not need multiple instances of msmtpd for this purpose, and therefore you need only one SMTP server in your mail client configuration.