A simple relay via OpenSMTPD
02 Mar 2017, updated: 24 Sept 2022
Using OpenSMTPD as a relay
through your favorite email service provider is quite an easy setup.
The first step is to of course install OpenSMTPD and OpenSMTPD-extras.
Do make sure to go through the
manual pages,
quite informative and useful.
The second thing we will need are the credentials to the email
service provider which are referenced under OpenSMTPD's configuration
file. The credentials file /etc/mail/secrets holds the
user name and password, along with a label of your choosing.
# touch /etc/mail/secrets
# chmod 640 /etc/mail/secrets
# chown root:_smtpd /etc/mail/secrets
# echo "bob username:password" > /etc/mail/secrets
The final step would be to edit OpenSMTPD's main configuration
smtpd.conf file like so:
# Table setup
table aliases file:/etc/mail/aliases
table secrets file:/etc/mail/secrets
# To accept external mail, replace with: listen on all
listen on lo0
action "local_mail" mbox alias
action "outbound" relay host smtp+tls://[email protected] \
auth
# Uncomment the following to accept external mail for domain
# "example.org"
# match from any for domain "example.org" action "local_mail"
match from local for local action "local_mail"
match from local for any action "outbound"
To make sure there are no syntax issues in the configuration file,
run the following command:
# smtpd -n
configuration OK
We then restart smtpd to pick up the new configuration. Command
below depends on what system you're running. OpenBSD system would be:
# rcctl restart smtpd
smtpd(ok)
smtpd(ok)
You may check to make sure it is working through the terminal with
the mail command:
$ echo "Message" | mail -s "Subject" [email protected]
One last tip depending on your needs, do make sure the
GECOS field is
properly configured for your local account.