Description
OpenSMTPD is a free implementation of the SMTP protocol, as defined in RFC 5321 , with some additional standard extensions. It allows the machines to exchange mail.
OpenSMTPD is a part the OpenBSD base system. It was ported to others OSes, as Devuan.
Informations:
- Website: https://www.opensmtpd.org
Q : Why do I use OpenSMTPD?
Because, OpenSMTPD is:
- easy to config : only one file text!
- recognized as reliable AND secure.
Fully functional and tested on:
- Debian Sid, Devuan Ceres
- Linux Mint
Installation
apt install opensmtpd
- the file log:
/var/log/mail.log
Configuration
- The file config:
/etc/smtpd.conf
To send a mail by SMTP to a mail service requiring identification, it is
necessary to first create a file secrets with the appropriate rights
on your system, then we have to configure the file smtpd.conf.
File secrets
To create the secrets file:
$ mkdir -p .config/mail
$ touch .config/mail/secrets
$ chmod 0640 .config/mail/secrets
Then, it’s necessary to write:
identifiant username:password
Do Not Write TEXTUALLY this information
,
replace with:
identifiant: your choosed id — this will use later on your config file.username: usually, your email.password: the password for your email identification.
It’s possible to (re?)name the secrets file as you want, and put in other place on your system.
It’s better put rights 0400 on this secrets file. Default: 0640.
Even, it’s possible for the service to access at your secrets file, with
your personal rights as $USER:$USER, it’s better to put the group right
opensmtpd.
File smtpd.conf
Now, edit the config file /etc/smtpd.conf
# $OpenBSD: smtpd.conf,v 1.10 2018/05/24 11:40:17 gilles Exp $
# This is the smtpd server system-wide configuration file.
# See smtpd.conf(5) for more information.
table aliases file:/etc/aliases
table secrets file:/home/your-id/.config/mail/secrets
queue compression
# To accept external mail, replace with: listen on all
listen on localhost
action "local" maildir alias <aliases>
action "relay" relay host smtp+tls://identifiant@server auth <secrets> mail-from "@your-domain.tld"
# Uncomment the following to accept external mail for domain "example.org"
#
# match from any for domain "example.org" action "local"
match for local action "local"
match from local for any action "relay"
Explainations
So compared to the original version, we added:
- the line
table secrets: it call the secrets file — write your custom filename. - the line
action relay: to define the necessary action to send emails to the server.- NOTE about
identifiant@serveur:- you have to replace the string
identifiantby your created. - and too, to replace the
serveurby the name of SMTP server.
- you have to replace the string
- the string
smtp+tlsis the used protocol to connect at the SMTP server. others protocols are:lmtp: to connect on a LMTP session.smtp: to attempt a connection with a STARTTLS session, if possible.smtp+tls: to force the connection on a STARTTLS session.smtp+notls: to use a plain text SMTP session without TLS.smtps: to force the connexion via TLS — default port: 465- with no specified protocol, the connection will be done on the default port: 25.
- the string
auth: to specify the secrets table. - the string
mail-from: to specify the domain name to use. - the line
match … action "relay": this is the action that will be triggered to send the emails.
- NOTE about
aliases
About aliases system:
It is interesting to manage the alias related to your root account or
even that of your main user…
Edit the file /etc/aliases, with rights admin.
At the end of file, modify root with your desired address email.
Do the same for your system user. ;)
And, do not forget to reload the aliases base, with the command newaliases!
Utilisation
Before restart the opensmtpd service, we need to test the config file:
# smtpd -n
If the result is: configuration OK
that’s folk!
Otherwise, re-edit the file, at the line indicated first!
Now, restart the service:
# service opensmtpd restart
Send
So:
echo "Test to send email on $(hostname); date: $(date)" | mail -s "Email test" email- or,
echo "Test to send email on $(hostname); date: $(date)" | mail -s "Email test" root
For all cases, the log will display messages, as:
(…)
Apr 27 09:16:47 pc-z smtpd[1718]: 09cca279ca1178e4 smtp connected address=local host=***
Apr 27 09:16:47 pc-z smtpd[1718]: 09cca279ca1178e4 smtp message msgid=85868a25 size=474 nrcpt=1 proto=ESMTP
Apr 27 09:16:47 pc-z smtpd[1718]: 09cca279ca1178e4 smtp envelope evpid=85868a25fcb1569a from=<my-id@***> to=<my-id@***>
Apr 27 09:16:47 pc-z smtpd[1718]: 09cca279ca1178e4 smtp disconnected reason=quit
Apr 27 09:16:51 pc-z smtpd[1718]: 09cca27892fa38ea mta delivery evpid=85868a25fcb1569a from=<my-id@huc.fr.eu.org> to=<email@nom-de-domaine.tld> rcpt=<my-id@***> source="192.168.47.47" relay="80.67.160.70 (lautre.net)" delay=4s result="Ok" stat="250 2.0.0 Ok: queued as 53C92112839"
Apr 27 09:17:02 pc-z smtpd[1718]: 09cca27892fa38ea mta disconnected reason=quit messages=2
(…)
Now, you can send email from console/terminal or yours scripts shell with SMTP authentification!
Errors
Look the different possible errors on my article OpenBSD: configure smtpd.conf to auth email client (≥ v6.4)
Documentations
The SMTP protocol defined by RFC 5321: