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OpenSMTPD is a free mail transfer agent, developed as part of the OpenBSD project. This article builds upon Mail server.

Note: Starting with version 6.4.0 OpenSMTPD depends on LibreSSL. Since libressl is still in testing, the opensmtpd package is stuck in version 6.0.3p1 for now. The opensmtpd-libresslAUR package from the AUR is available for newer versions.

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: There is no indication that opensmtpd will get updated any time soon, so it would be more useful to rewrite the article to use use opensmtpd-libresslAUR. That includes using the new configuration file syntax introduced in version 6.4.0. (Discuss in Talk:OpenSMTPD#)


Install the opensmtpd package.


OpenSMTPD is configured in /etc/smtpd.

Note: Starting with OpenSMTPD version 6.4.0 the configuration file syntax has been completely reworked, breaking compatibility with previous configuration files. The following examples are for old version 6.0.3p1.

Local mail

To have local mail working, for example for cron mails, it is enough to simply start smtpd.service.

The default configuration of OpenSMTPD is to do local retrieval and delivery of mail, and also relay outgoing mail. See smtpd.conf(5).

Local mail only

To do only local mail, the following is enough:

listen on localhost
accept for local alias <aliases> deliver to mbox

Hybrid : local mail and relay

These two lines in /etc/smtpd/smtpd.conf :

accept for local alias <aliases> deliver to mbox
accept for any relay via "smtp://" as ""

configure OpenSMTPD to :

  • send local email locally, without going through a relay (useful for cron & at mail notifications)
  • use a relay to send a mail outside of localhost

Simply replace by your ISP mail server, or another server at your convenience.

Relay only

To send all local emails through a relay invoke procmail:

accept from local for local virtual <aliases> deliver to mda "procmail -f -"
accept from local for any relay via smtps+auth:// auth <secrets> as "foo@bar"

The aliases option is used for the local user mapping, for a simplified mapping you can use virtual aliases with a catch all:

@ foo@bar

Simple OpenSMTPD/mbox configuration


To obtain a certificate, see OpenSSL#Usage.

Note: OpenSMTPD has solid defaults, SSLv3 is always disabled and the default ciphers are not known to be insecure. You might still want to test the server as described in Server-side TLS.

Create user accounts

  • Create a user account on the mail server for each desired mailbox.
# useradd -m -s /bin/bash roger
# useradd -m -s /bin/bash shirley
  • OpenSMTPD will deliver messages to the user account's mbox file at /var/spool/mail/<username>
  • Multiple SMTP email addresses can be routed to a given mbox if desired.

Craft a simple smtpd.conf setup

  • A working configuration can be had in as little as nine lines!
pki mx.domain.tld certificate  "/etc/smtpd/tls/smtpd.crt"
pki mx.domain.tld key          "/etc/smtpd/tls/smtpd.key"

table creds                    "/etc/smtpd/creds"
table vdoms                    "/etc/smtpd/vdoms"
table vusers                   "/etc/smtpd/vusers"

listen on eth0 tls pki mx.domain.tld
listen on eth0 port 587 tls-require pki mx.domain.tld auth <creds>

accept from any for domain <vdoms> virtual <vusers> deliver to mbox
accept for any relay

Create tables

  • For the domain table file; simply put one domain per line
  • For the user table file; list one inbound SMTP email address per line and then map it to an mbox user account name, SMTP email address, or any combination of the two on the right, separated by commas.
/etc/smtpd/vusers          roger    roger,            roger          shirley             roger,shirley
  • For the creds table file; put the user name in the 1st column and the password hash in the 2nd column
roger                              <password hash created using 'smtpctl encrypt' command>
shirley                            <password hash created using 'smtpctl encrypt' command>

Test the configuration

# smtpd -n

If you get a message that says 'configuration OK' - you're ready to rock and roll. If not, work on any configuration errors and try again.


Console debugging

If you're having problems with mail delivery, try stopping the smtpd.service and launching the daemon manually with the 'do not daemonize' and 'verbose output' options. Then watch the console for errors.

# smtpd -dv

Subsystem tracing

Add the -T flag to get real-time subsystem tracing

# smtpd -dv -T smtp

Alternately, use the smtpctl trace <subsystem> command if the daemon is already running. The trace output will appear in the console output above as well as the journalctl output for the smtpd.service. For example:

# smtpctl trace expand && smtpctl trace lookup

...will trace both aliases/virtual/forward expansion and user/credentials lookups

Manual Submission port authentication

  • Encode username and password in base64
# printf 'username\0username\0password' | base64  
  • Connect to submission port using openssl s_client command
# openssl s_client -host mx.domain.tld -port 587 -starttls smtp
  • enter ehlo myhostname followed by AUTH PLAIN. Paste in the base64 string from step above after 334 response.
250 HELP
ehlo test.domain.tld
250-mx.hostname.tld Hello test.domain.tld [], pleased to meet you
250-SIZE 36700160
250 HELP
235 2.0.0: Authentication succeeded

"Helo command rejected: need fully-qualified hostname"

When sending email, if you get this kind of messages, set your FQDN in the file /etc/smtpd/mailname. Otherwise, the server name is derived from the local hostname returned by gethostname(3), either directly if it is a fully qualified domain name, or by retreiving the associated canonical name through getaddrinfo(3).

See also